If you can't afford the slip yoke yet,don't worry ya don't have to cut much just a lil trim on the backside of the 4wheel shift lever. don't forget to weld up the holes on the frame rails where they bend up in the front.factory weak point.
check the pullys make sure there is not an inward bend in them to allow belt to climb out and throw itself at high rpm's. had a 350 crank pully that had small inward bend that didn't notice right away kept throwin belts too.
If it's got a factory alarm system it could be having an issue brain won't let the feul pump or coil fire. Might need to trick the alarm system some how.