I know this threads old but I figure it would be best fr me to post here instead of having useful information in 2 places. I have a 95 s10 Zr2 manual trans. W vin engine code with side mount pugs on Dist.. Engine spun a bearing and i found a 1995 Automatic Blazer 4.3 W engine with top mount plugs on Dist.
After much confusion and days of reading I believe swapping the Reluctor wheel, timing cover with crank sensor, lower intake manifold and distributor from my old EDI engin on to the HEI this would be everything needed to essentially "convert" the donor top mount plug engine to the side mount application I need. Can anyone correct me if i missed anything?

 

BTW both engines have the plastic 6 bolt hole timing covers. Only other thing listed in a manual was 2 strut bosses added for transmission support. Anyone know where those can be located so I can try to verify a complete block match.