motor buildup problems

[dragonwingstoy]

well im running into a slight problem with my motor buildup that i have been doing, i have a 22r block that i had gotten with the pistons with it but nothing else and had blown a connecting rod through the side of the 20r that was in it, i have been using the internal parts from the 20r in the newer block but when i went to put the timing chain i have run into a problem,since almost all the parts in the old motor seemed to be newer i have just been reusing what was still in very good shape on,
I cant get the timing chain to go tight enough on it, and after a while i had decided to measure the top to bottom length of the block and have found the problem the 22r block is 1/8 to 1/4 inch (couldnt get an exact measurement on it) shorter than the 20 r.
now im wanting to know if i can get the timing chain for a 22r and have it fit right? one problem is though i have no clue what year the block is only thing i have on the block number from the side of it. can anyone tell what year it is from that block #?
#2538157 22r
thanks in advance for any help