I think the earlier heads both 2 and 4v were higher compression than the later versions were after the
oil imbargo and the low octane fuels they threw at us
The 2v head is the best cleveland head for a driver and even it has a tendency to run better at higher speeds. There was also some changes made to the way the rocker arms fastened down if I remember right
You can take your flywheel to a balance shop and have them put weight on it to nuetral balance and then transfer that to another flywheel to see if it zero balances which will identify what weight it is???? I do it all the time on questionable flywheel/clutch changes, its just hard to explain ---
the 6619 holley is a good choice and all the holley tuning tips work fine--