On a mild engine buildup, figure on about a fifteen-twenty horsepower difference between a 272 and 292 when all else is equal. Here’s the link showing some horsepower numbers for a 272 that’s built on the mild side.
http://www.y-blocksforever.com...
This particular engine is in a ’54 Ford F100 and provides a significant power increase over the original 130HP V8 that was in the truck.
The new main bearing sets for the 312’s are double the price of the main bearing sets for the 272/292 engines so this is just one consideration. Unless you’ve already got a rebuidable 312 on hand, finding one may prove to be a problem without paying more than it’s worth. But using the 312 crankshaft in a 272 or 292 block is a very viable option for a variety of reasons if you can find just the crankshaft. The oversize pistons for the 272’s are getting more difficult to find as an in stock item so this is also a consideration when attempting to rebuild a 272. My definition of a short block rebuild includes connecting rod reconditioning, new pistons, boring, decking, align honing the mains, new cam bearings, and vatting among other things. The cost of this is obviously considerably more than a re-ring and a fresh set of bearings. Costs will vary depending upon the machine shop prices and where the parts are purchased. The region or area of the country is many times a player when it comes to costs. Be sure to ask your friends and acquaintances regarding quality from the shops you expect to deal with. No need to duplicate someone else’s bad experiences.
Because the 292 engines were used heavily in the car lines thru 1962 and pickups and trucks thru 1964, these are the easiest Y’s to find. Having a 272 on hand already then calls for a decision of whether to start with this or go for the larger engine. One of the reasons to go for another block or engine for a rebuild is so that the vehicle is not down as long which is what I typically recommend and especially if the vehicle is still running. It’s just a simple matter of pulling one engine and replacing it with the other. If finances are tight, then using the current engine for the rebuild eliminates the need on purchasing a core engine.

Lorena, Texas (South of Waco)