Magnum head and exh manifold ID

2 types of magnum heads 1 for 318's the 302 casting no. and a different head 308 casting no. for the 360 head. I beleive the 318 head is 188 in. and 165 ex, valve size the 360 head is 192 in. and 165 ex valves. The 360 head has 360 size ports and the 318 has has smaller ports and a slightly smaller combustion chamber. Overall the 360 magnum head is excellent, but you will also need new lifters and push rods with a new intake manifold.
Exhaust maniflods were the same 318/360 although I beleive the 98 up manifold's were slightly better.
Van year - Usually the sticker on the drivers door says prodution date.