I recommend upgrading to a 200R4 or 700R4. You get four speeds, with the top one being an overdrive. You do need to install an electronic module in it since we don’t have a computer in our vans! (Not very difficult.) 200R4 does not require shortening the driveshaft but I went with the 700R4. On the latter, avoid the early models. Do a Google search for the year range of the better ones.
You can read the whole long story of my conversion to a 700R4 tranny here. I fabricated a tranny hanger much like the TH350 hanger. (Don was nice to loan me his for inspiration.) I like how clean and out of the way it is:
https://vintage-vans.forumotion.com/t1038-back-to-vanagains-newest-65-chevy-sportvan-deluxe#5330
And I made a mount for a 200R4 you can see here. Note the simple cuts we made in the crossmember to add clearance so we didn’t have to lower the tranny (and engine). I wish I’d done that on my 700R4.
https://vintage-vans.forumotion.com/t24747p75-scotty-s-1965-chevy-sportvan-deluxe-travel-cruiser#131577
The hardest part was making a way to hook up the TV cable to the carb lineage on a 6 cylinder. If you have a V8, there are many brackets available for popular carbs.
You can read the whole long story of my conversion to a 700R4 tranny here. I fabricated a tranny hanger much like the TH350 hanger. (Don was nice to loan me his for inspiration.) I like how clean and out of the way it is:
https://vintage-vans.forumotion.com/t1038-back-to-vanagains-newest-65-chevy-sportvan-deluxe#5330
And I made a mount for a 200R4 you can see here. Note the simple cuts we made in the crossmember to add clearance so we didn’t have to lower the tranny (and engine). I wish I’d done that on my 700R4.
https://vintage-vans.forumotion.com/t24747p75-scotty-s-1965-chevy-sportvan-deluxe-travel-cruiser#131577
The hardest part was making a way to hook up the TV cable to the carb lineage on a 6 cylinder. If you have a V8, there are many brackets available for popular carbs.