I'm finally getting my son's Y-block back together and I just have a quick question. The engine will be fuel injected, so no need for the fuel pump eccentric or the counterweight that goes with it. Can I just replace the two pieces with an equally sized spacer or should i just put them both back on? FWIW it's a Rollmaster chain with a Mummert (Clay Smith) 270 cam.

i would put them back on in case down the road you or someone decided to go back to a carb.

Darrel makes a good point about retaining the fuel pump eccentric and counterweight for a future application where those pieces might be required.  But if determined to do away with them, then ‘Yes’ in making an appropriate spacer to do away with them.  Be sure to broach or machine an appropriate keyway slot so the new spacer it will fit up flush to the cam gear.  Here are a couple of pictures of what I have done.
 

 

Lorena, Texas (South of Waco)

any idea ted how many y blocks you have rebuilt.

Decided to leave them in place. You did make a good point Darrell.
Sorry about the sideways pic. I have no idea why it did that.

I’ve no idea how many Y’s I have put together over the years.  Looking at the balance job records, there has been 95 Y rotating assemblies balanced since 1985.  Looking at the dyno records, there have been 89 different Ford Y-Blocks on the dyno since 2008.  The dyno mule (a +060 over 312) by itself has almost a thousand dyno pulls so the total number of Y pulls has to be astronomical.  Being also a FE guy at heart, the number of FE’s far outstrips the Y stuff that I work on.

Lorena, Texas (South of Waco)