Couldn't the bolt on yoke be removed and a slip yoke type drive shaft be used instead ?....a friend used a TH400 that had that bolt on yoke,from a P-30 step van, in his Olds Cutlass (that had a Chevy 350 in it) and did just that and it worked out fine...it would be easier to find a car or 2wd truck shaft and cut it if need be,much cheaper than a custom one..
Here,finding a good used drive shaft is next to impossible,ever since junkyards started using fork loaders to move vehicles off the trucks that hauled them in...nearly every one gets dented or buckled up..