Much of this likely depends what you ultimately would like performance wise.  The Isky E4 is a good all around camshaft with just enough rumble to let you know the engine has a camshaft in it.  The Isky RPM-300 is definitely a better performer but is expected to be a tad softer in performance right off of idle and part of that will be associated with the 112° lobe centerline it is ground on.  If I was special ordering this camshaft straight from Isky, I would specify that it be ground on 110° lobe centers.  At 3000 rpm and with 112° lobe centers, it is expected to come on much stronger than the E4.  My ’55 Customline with a 272 has the E4 and idles good while still being a good all around driver.  The 312 I use as a dyno mule has the 238/238 Crower camshaft ground on 110° lobe centers and it also idles good with a noticeable rumble but is strong with mildly ported G heads well past 5500 rpm.  The 312 dyno mule also uses a Mummert intake and 750 cfm Holley carb.  Considering the weight of your car along with the transmission and gearing, I would lean towards the Isky RPM-300 with a 600 or 750 carb if looking for a good compromise between daily driver and good performance.  Regardless of what camshaft you select, take the time to degree it in to insure it is installed exactly where it needs to be.  4-5° of advance is typically recommended with a new timing set in place.

Lorena, Texas (South of Waco)

Thanks for your thoughts, I guess it is coming down to the E4 or the RPM-3000. Can you confirm that the RPM-3000 is the ISK 301333? I also have to go back and check the cam card on the cam that is in the car now. I always thought it was too much cam as it did not pull real good until over 2500 RPM but that is with a Ford-o-matic and I did not degree it in. I will be sure to do that this time.

See if this helps.
 

Lorena, Texas (South of Waco)

YES, like always, Thanks

I have an Isky 301333 cam in TBird.  My engine is a near stock 1957 292 bored .060", iron 312 intake, Holley 4V and a manual transmission with O/D.  I love this cam.  It has a noticeable lope at idle, just enough so you can hear the cam pop through the tailpipes.  Low RPM torque is good, mid range is outstanding. The only modification I made was to cut the cam oil grove to .030" deep.  It pulls hard to 5,000 rpm.  I have never revved my engine higher than that. If you want a quiet engine, this cam may not be for you.  If you want a muscle car sound and feel, I think it's perfect.

Great, Thanks Phil, you and Ted are making this easy.

If I have not made it clear, I have a running 292 in the car now, i'm just building another one that will be a little better. So as far as cam selection goes,
   What I have in the car now,   .471 lift     224 In/230 Ex duration at .050 lift  108* LSA
The thing is this lift is way more than other cams I have found
ISKY  2000-5000rpm  .425 lift w/ 216* duration at .050 lift   108*LSA
ISKY  2500-5500rpm   .448 lift   w/ 228* duration @ .050     112* lsa
ISKY 3000-6000rpm    .448 lift  W/250* duration     108* LSA
Clay smith 1800-5500rpm  .440 lift w/ 224* duration   110* LSA
Clay smith 2000-5000 rpm    .446 lift w/224*     108* LSA
Clay smith  2500-6200rpm .462 lift  w/236*  108* LSA
Howard 1800-5000 rpm     .463  w/ 220*  110*  LSA
Howard  2800-5400rpm      .515  w/238*   110*lsa

Now I have found some info on Isky’s site and Munnert’s site that says I must cut the valve guides when using a can w/ lift more than .450” as you can see the cam in the car is .471 lift and I did not cut valve guides and this set up has been on the car with two different heads.
 I have also read that less LSA gives a more choppy idle, more lsa gives a smooth idle. I would hate to give up my idle sound. I guess the CompCams Camshaft I have in the car now is closest to the 2000-5000 RPM Clay smith cam but with less lift. 
Any thoughts? 

You will want to look at lobe lifts on the camshafts when comparing different cam grinders as everyone may not be using the same rocker arm ratio for the valve lift calculations.  By looking at the lobe lifts, you can multiply it by whatever rocker ratio you are using to get a more accurate feel for what is happening at the valve.  Keep in mind that you will want to subtract the valve lash from any calculated valve lift in order to know the actual valve lift.
 
As far as what your heads can handle in regards to valve lift, that is typically determined as they are being assembled.  If they have been machined for positive type valve seals, then different shops machine the tops of the guides at different depths so that’s an unknown until you actually measure the retainer to seal clearance.  Assume nothing.

Lorena, Texas (South of Waco)

True but most if not all the cam specs I have listed calculated valve lift with 1.5 ratio rockers ( I think one did not specify ratio) and the heads that have been running with that .471 lift cam are stock heads with stock style valve seals. I'm thinking that the .471" lift number may be a misprint, guess I could measure valve travel and see.  so is it true that on most Y block builds if you have more than .450 lift at the valve you will need to cut the guide some?

Stock ECZ-G and ‘113’ heads with the factory rotator valve spring retainers have ~0.430” between the retainer and umbrella seal.  This is before any grinding on the valves and/or valve seats which will increase that measurement.  If using a single piece retainer, the clearance between the retainer and seal will increase to ~0.460”.
 
These measurements only deal with what the cylinder head can tolerate in the way of valve lift.  No safety margins for valve float are included.  Additional consideration must be taken when dealing with the intake valve in relation to clearance at the edge of the cylinder wall.  I typically use 0.535” of intake valve lift as the limit for that.  How much the heads are milled and/or valve diameters can have that value varying.

Lorena, Texas (South of Waco)