I've done a little research on the subject in the last few months since i've been having problems with my '46 1/2 ton torque tube joint (and had problems with the torque tube joint in the '50 1/2 ton I had, too).. both vehicles have the splash oil 216 and stock tranny & rear.
Everything i've read suggests that a 216 or 235 with an updated rear, and an open driveline SM420 gives you far better top end speed and makes the vehicle more 'daily drivable' at contemprary speeds.
No doubt in my mind that a later full pressure 235 will be sufficient.. slapping a V8 in there just sounds like a huge headache, more money, and longer wait till you can drive your truck again!
Everyone i've talked to who's used the t5 behind an inline 6 has loved it.. altho from what I understand it takes a little 'engineering' to get it to work.
I think the SM420 is pretty much a driect bolt in swap.. and i'm all about easy.. so when I finally get sick of the torque tube BS in my 1/2 ton, thats probably the route i'll go.
In my opinion.. half of the 'cool' factor of my '46's is the way that old I6 motor sounds.. and I wouldn't get rid of the stomp start for all the tea in china.
As far as workability, I can put 3,000+ lbs of corn in the back of my '46 1/2 ton and putt right down the road with a splash oil 216 and stock 4 speed (altho the back end squats down quite a bit!) that combo was built to work, and that 1st gear has enough grunt you can pick up some extra cash by offering a tree stump removal service.
But if I were doing alot of highway driving, I might consider going the t5 route.. guess it really depends on how you'll be using/driving the truck.
