question regarding main bolt caps matching blocks that had steel crank and cast

[SeattleCharger]

Hi, I bought a 72 engine to get the steel crank out of it.  Then I sold that bare 72 block to a guy.  I kept the main caps because they are different than the main caps I have for the 77 block I was going to put the steel crank in. 
   I thought the 72 main caps should go with the 72 steel crank, and that the steel crank main caps must be better or something, so I kept them.  Now he wrote back that the 72 block is useless without the main caps that were on it.

  Can I use the 77 block with the 77 main caps I have (had cast crank in it) with the  72 steel crank?      I guess I would give him the 72 main caps if they are useless to me.  Thanks for any help.

    This is the email he wrote me:   

       "nate hey do you still have the origonal main caps to that 72 440 i bought from you, little foiod for thought you cant use the maincaps on another block due to specified machineing at the factoy when the block was cast and machined, this was told to me by a well know engine builder,so if you have them and you havnt put the 440 together, you should cosider getting the block back from me or giving me those main caps which are useless to you, and this block is a useless part for me not being able to be matched up with new mains, the 72 block i got from you actually is the beast block to make a stroker from the 72 had reinfoced vains through block and a reinforced casting, which makes them better, i had to give a guy my 67 440 shortblock to do his motor due to the non origonal maincaps i have, so let me know  what we should do  thanks"

   

[FLG]

Im not an expert but it dont make sense

If your building a stroker, you would more then likely NOT use the main caps that came with the block...heck you wouldent use stock main caps at all. You would go online and look at aftermarket caps which would be stronger then stock caps and be able to withstand the horses a stroker block puts out.

[Challenger340]

Keep the Main Caps, ON THE CORRECT BLOCKS, that they were mated to at the Factory.
Buddies Builder is telling the Truth.
It's more of a real Pain in the Ass to re-machine and fit different Caps in a Block, so usually it's only done if using Billet Aluminum, or other upgraded Pieces.

A Forged Crank will go in any later year Block, just use the correct Main Bearings for the Year of Block you are using,
also,
Absolutely NO STRENGTH difference between years of Main Caps.

Send Buddy the '72 Caps, they are useless to you.

[FLG]

Keep the Main Caps, ON THE CORRECT BLOCKS, that they were mated to at the Factory.
Buddies Builder is telling the Truth.
It's more of a real Pain in the Ass to re-machine and fit different Caps in a Block, so usually it's only done if using Billet Aluminum, or other upgraded Pieces.

A Forged Crank will go in any later year Block, just use the correct Main Bearings for the Year of Block you are using,
also,
Absolutely NO STRENGTH difference between years of Main Caps.

Send Buddy the '72 Caps, they are useless to you.

Learned something new, thanks 

[SeattleCharger]

Allright.  Thank you.   Sure he'll be happy to get them, and I'm good knowing I am not giving away some valuable part that I will regret later.   Thanks again.
Nate