I have another suggestion for your towing '49:
Why don't you look into the modern 6.0 liter engine from current Chevy/GMC trucks, and trans?
New 1-ton trucks use this engine, they give you modern reliability, good mileage and, rated at over 300HP, they sure haul! This engine is also smaller than a big old Cad, and even easy to mount if you use a front clip: either an aftermarket front clip can be bought with the right motor mounts, or an older V8 clip (Camaro, for instance) just requires a pair of engine mounts adapter plates. Easy!
The electronics part is also easy (yes, really!): you can have the OEM harness modified or buy an aftermarket one (I have used a place called Speartech for this, great guy!).
You could even use one of those newer 6-speed auto trans, or just the 4L80E (which is an electronic TH400 with OD).
Old engines are cool, but you need power and endless reliability (especially for heavy use), you can't beat a modern engine!
