Steve,
Good point about the trailer. I am always on the iffy side of the T5s. That is why I put a NV4500 in my 59, and plan to do the same in my 1940. Having actually gotten dirty and installed one I will have to say it is a big effen transmision that ways about 200 lbs and costs between $4 and $10/ lb. That is to say it is not cheap. I would absolutely reccomend this transmission for a built up inline engine that sees heavy towing or 4wd action. But it is a spendy option. You can get used NV4500s in the $600 range, rebuilt starting at $800 with a $300 core, or about $1800 for a brand new one. You will still have to get an adapter or a new bellhousing, cut the driveshaft or have a new one made, and callibrate the speedometer, which depends on weather you are using an electronic signal or a mechanical signal.
There is nothing better than a 5 speed with granny low and overdrive for towing save the Gear Splitter system that Macdaddy mentioned. With that system you have 8 forward gears, so you could virtually shift between the gears to find the engines sweet spot on any grade. By the way, it would also work on a NV4500 giving you 10 forward gears, but that may be overkill.
Anyway as mentioned there are many options for you. Decide weather you want auto or stick, and how much you want to spend, and we'll walk you through the pros and cons of it all. It can get expensive really quick.
