302 vs 5.0L
According to my "Ford Windsor Small-Block Performance" book 302 blocks cast up to 1974 (D4 casting prefix) have greater material thickness and are good candidates for 4-bolt main conversions. However, until 1981 Windsor engines had two-piece main seals that can only be replaced by removing the crankshaft. Also, starting in 1985 roller cams were installed in the 5.0L. Lifter bores were lengthened for the longer roller lifters.
I suggest using a 1985 or later block for a 347 stroker kit short block. I assume that you're aware of the external balance issues associated with upgrading the Explorer to a 347. The stroker kit is designed for the Mustang 5.0L with a 28 inch-ounce front balancer. The Explorer is fitted with a 50 inch-ounce front balancer. You'll need an Explorer trigger wheel mounted on a 28 inch-ounce balancer (of the correct diameter) and a Mustang flexplate/flywheel or a machine shop will have to remove metal from the crankshaft counterweights to balance the engine. I'm not aware of any 347 stroker kits designed for the Explorer 5.0L configuration.
