Different intakes for different engines/heads

[Kalums]

Ok guys I've got a 71 GMC K2500 with a 350... But the 350 seems to be a "Target Master" from the 80s or 90s... However it does have an original cast iron spreadbore intake (which is leaking from the front coolant "pass through/chamber" (only visible once engine has heated up and is currently just seaping. I plan on replacing the Eddy 1406 with either an original (rebuilt) Q-Jet or a spreadbore Holley 80555C. Question is... Edelbrock performer 2101 (old style mid 60s heads to mid 80s)or Edelbrock 2104 designed for 80s-?90s heads? I'm not 100 percent sure exactly and can't find too much info on the internet... My "search" skills are lacking. How do I tell what I need? My understanding is there is a different "slant" on the center bolts? I honestly don't know. Or can anyone suggest a good intake for a spreadbore? Any help would be appreciated.