I am new to Oldsmobiles, although I did restore a 1951 88 convertible back in the 90’s. I am now considering a project to put a 455 in a 1949 body, and I am finding out that there are different blocks and heads for different years. I want to build a mild rat rod sleeper, and I am looking for advice on which blocks and heads would be best for this. I plan to buy a used motor to rebuild, and I would like to buy the best 455 for my plans.

 

Welcome. If you plan to rebuild the 455, it really doesn't matter which one you start with. Olds varied compression with the pistons, not the heads, so just pick the pistons with the CR you want. There are really only two different 455 blocks that you will come across, the F and FA castings. The F block was used from 1968-74-ish, the FA from 1973-76. The only real difference between them is that the FA block does not have the boss for the clutch Z-bar pivot. This is a non-issue if you plan to run an automatic.

Pretty much all 455 cranks are cast nodular, which is fine for all but the most extreme builds. The forged 455 cranks are extremely rare and priced accordingly when you come across one.

With the exception of the 1973-76 "J" heads, all Olds heads flow within about 5% of each other in stock form. You'll find volumes on the web about which Olds heads are the best. Most of that is BS. Unless you plan to have port work done (in which case it really doesn't matter which ones you start with), just have a good valve job done and get the big valves installed if they don't already have them.

Pick a cam to match your intended use. The rest is all pretty straightforward engine assembly. Good luck.

 

To follow up on what Joe wrote; C and G heads aren't too hard to find. I'm in the middle of my 455 build right now and got lucky with a set or re-worked J heads, bolt-on ready. Just need to have the new springs pressure tested. They're basically C heads now, but with the smaller valves.
The Facebook "Oldsmobile: Buy, Sell, and Trade" site is a good place for finding parts. As is, placing an ad in this site's "Parts Wanted" section.
Are you stripping the short block and having machine work done?