273 302 318 340 build

So a little more info. Rods in 83 318 are 3418645 which books tell me stock and press fit.
70 318 con rods are 2406782 stock but not sure if press fit or floating I havent put it on stand yet.
I only have one engine stand so its a pain in the arse at this stage of the game.
Are the 83 rods better than the 70 rods? Should I pull the 83 ones before I put 70 on the stand?
Also pistons...the Sealed Power ones I was looking at are press fit. Can you convert floating to press fit?
Without major costs?
Thanks!