yes 5/6/7m blocks are all interchangeable. performance studs were never made for the 12 valve head though, 7mgte arp studs with ball bearings in the block to keep them up high enough to compensate for the head thickness, or the nuts will never get full thread. is a 5m block better than a 7m block? i would say no, almost the exact same block EXCEPT the connecting rod and crank change from the 2m (2.8L 5mge) to the newer 6m (3L 6m/7m) crank starting some time in 1986 i think? dont quote me on the exact date...
then again in 1989 the 7m blocks received a newer crank the 7m which is also a 3L crank almost the same as the 6m, BUT cylinders 2 and 5 got counter weights for the pistons, resaulting in a max RPM change in 1989+ models.
now, the 2m crank stays the same for 5mge 2.8L models until mid 1984 where all 84to86 5mge 2m cranks got slightly different bearings.
comparing the rods i would say 5m rods are the weakest, the 7mge rods have stronger bolts, and the 7mgte rods are just a little bit stronger than than.
i would also like to point out that a 5mge 2m crank snout is smaller and thinner in diameter than a 7mge 6m crank snout.:
