Skippy - being the only up north Islander posted on this thread, I won't take any offense at your not making bonehead mistakes

I not only agree the spray foam is a bad idea [and unlike many bus converters, I won't use it], I agree most folks are just expecting too much from these old workin mens trucks as a result of spending most of their road time in new cars .... OTOH, the bubble pak stuff does pretty well in a lot of places, with a bit of spray can undercoating to hold it in place
the way to deal with those gaps you've wound up with is some judicious bending with 2x4 in the door opening, the TF series is a particular problem that way, with the dogleg - I doubt any [well many] of them came off the line with those gaps .... of course the time to do that is well before final assembly and paint, but with care it can be done on the finished truck, doubled or tripled weather strip won't hold up long if you're really gonna use the doors much, and looks goofy
Bill