other than the dash, 55-59 cabs Chev/GMC can be interchanged ... the 58/9 firewall is slightly different [aside from the hood hinge mount holes, which can be modified]
hoods: 55/6, 57, 58/9 [55-7 Chevy hoods fit 55-7 GMC, but are different, the GMC hoods have an opening in the front ... 58/9 are the same either make] 55-7 hoods will NOT fit between the 58/9 fenders and vice versa .... many seem to prefer the 57 hood on the 55/56's
fenders: 55-57 Chev or GMC the same except for some grill area holes - 58/9 the same for both makes
inner fenders: 55-7 Chev or GMC, 58/9 Chev or GMC
doors: 55-59 the same for both makes
+ the 58-59 frames are about 2" longer at the front, can't easily put 58-59 sheet metal on the earlier frame, and to put the earlier sheet metal on the later frame it has to be cut back
so technically the groupings are:
cabs, 55-57 Chev, 58-59 Chev, 55-57 GMC, 58-59 GMC
hoods, 55-56 Chev, 57 Chev, 58-9 Chev or GMC, 55-56 GMC, 57 GMC
fenders, 55-56 Chev, 57 Chev, 58-59 Chev or GMC, 55-57 GMC
inners, 55-7 Chev or GMC, 58-9 Chev or GMC
doors, 55-59 Chev or GMC
Bill
