A GM 4.8 (LS) piston will fit with a 6.7" rod and a little work, this gets you a modern ring pack and cheap pistons. 

I don't know how bad you need it or what your willing to pay but I would contact Ross Pistons in I believe El Segundo Ca. Go to their website an see they make custom pistons for flatheads and FE's plus all other  Fords even though they don't show a Y-Block. They've made me custom forged pistons for my race and street GMC's. If you send them one I'm sure they could copy with the same weight from one of their other forging. That what I did for my sons engine gave them one to copy and they made 6.  You need to make the ring package is the same if you already have the set..
I just bought a single Silvolite CAST off E-Bay for a std 312 and honed out a 292+.040 and extra .010" and was lucky it was 3 grams light and works great. Even bought std rings too.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

They show up on E Bay once in a while, also look for 1831PX (Sealed power) the X means forged, 

i have a 56-57 292 block that has been bored .050 or 3.80. 

REX HP told me the TRW L2018F has the same profile as a factory 312 piston. so using a EBU or C2AE rod, the piston will sit a bit below deck and with G heads, i'll end up with a static compression ratio of 8.4:1
they said advertised compression is 9.0 but in actuality, it's more like 8.4

the old TRW piece has the stock 312 profile so that it can be used with either crank. i have a forged C1TE truck crank and am looking for a set of C2AE rods also.

a standard 283 piston is 3.875 which would require i go an addition .075 or a total of .125 over the stock 292 3.75 bore. too much.

i need a set of forged L2180F in standard bore size of 3.80

I run 312 blocks with 312 cranks, no problems, I never turn down 312 cranks to fit a 292 block, I worry about overlap (main to rod journal), it's bad enough when I turn down a rod throw to fit a aftermarket rod.

Excellent thread. I only wish I would have known all this 7 years ago when I dropped a 312 crank in my 292.   I could have saved .023" of good iron from both decks. After removing that amount from each deck, the pistons were still .009" in the hole.


64F100 57FAIRLANE500

With 312 rods and a 312 crank (ECZ) you don't have to cut the piston tops, the deck height is about right as is, if you buy aftermarket forged pistons the rods do not need to be narrowed and will be full floating (no need to cut for pin retainers) and yes they still make standard sizes.

The stock bore of a 283 is 3.875. The stock bore of a 265 is 3.75. A stock bore 292 Y-block would have to be bored .125 for standard-bore 283 pistons. There's also the issue of compression height and rod length.

As No Shortcuts stated, I have an engine with 283 pistons with a 3.750 bore, standard 283 size.  The rod (C2AE/292) small ends had to be honed to .927 for the 283 pins, grooves cut in the piston pin holes for lock rings, the pins shortened to accommodate the lock rings, and the piston tops machined to Y pin-to-top dimension.  The Y rod small ends  were too wide to fit in the pistons, and were narrowed to fit.  I didn't have my Bridgeport mill then, or I would have machined the inside of the piston for clearance. Actually, I went with 0 deck height, so the piston tops were measured during pre-assembly and machined for 0 deck.  The valve pockets were not considered a problem, the machining eliminated much of the pockets.  A plus to this was the top piston ring moved up in the bore.  I was able to do all the machining, except honing the pin bores, myself, otherwise this would have been too expensive had I hired the work done.  Custom pistons would have been a better choice.  I did this because I used an ex stock class block that was already .060 oversize and worn.  The engine is in my F350 car hauler and is still doing fine after several years and thousands of miles. 

John - "The Hoosier Hurricane"