On the instructions that came with my Edelbrock carb the front vacumn port is designated for the PCV hose and the rear for power brake vacumn. Can the rear port be used for PCV?

i use the one in rear for the power steering's brake boost vacuum.

the front i use for CV, its just closer.

look at the porting for the holes on under side the carb. they will tell you what pull from manifold vacuum.

I used the one on the front for the pcv and plugged off the one in the back and used the port on my air gap intake for the power brakes!

yes you can

front or back for brake booster or pcv valve

you can use a port in the intake for the booster also

its all manifold vac in these 3 spots

the dist vac would go on the pass side of carb looking at it

the other side is full manifold vac and I use it for a S&W vac gauge I installd in the cab