New to Small Blocks - Info needed to help me make a decision

No deck height diffences or cam height differences. Since this is why in a big block right? Not so with the smallblocks.

Theres a few internal differences. Like a 360 pan fits a 360 only and the others can swap. 340/360 drivers mount are not the same as the 273/318's. You can swap on a 318's to the 340/360 but not the otherway around, there to narrow.

A 1 year only 340 and all 360 are extrnal balance. All 318/273 are internal and all the 340's except 1973's extrnal balance which is not the same as a 360's BTW.

PAY ATTENTION to header fitment notes with a 727 and a small block.
Sometimes some headers are a no go due to the extrenally larger 727 or the 904.