Re: powerhead swap
You're wanting to put the 1979 powerhead on the 1976 midsection, right?
If so, yes, that will work. You'll have to change the thread location for 4 of the mounting bolts (2 on each side). Simply get the base gasket for the 1976 85 and put over the base of the 1979 powerhead. You'll see what has to be done. No big deal, some places have a jig to do the conversion.