If the firewall problem can be resolved, the center mount turbo should spool better with the free flowing, and balanced exhaust gasses....

 

except the vans intake is very restrictive

 

the problem with using the center mount heads on a 6.2 is the injectors are at a differnt angle, and the intake manifold bolt holes are a different angle, so you would have to use the van intake, and turbo, not a side mount, or N/A intake.. i used military 6.2 heads on my 6.5 and the power differance was amazing!! but if you do- MAKE SURE to use THICKER head gaskets!! to keep the C/R at 21.5-1 i used .010 thicker head gaskets.. i also had to rebend the fuel lines.. its a pain to do and not kink them.. i also wraped them in some "split" vacuum tubing to keep the lines from rubbing anything.. if you have the heads off already, and have "J-code" 6.2 heads laying around- i say go for it!