Mine are all semi-auto bikes. A manual clutch motor is cheaper to buy on eBay although you can go crazy and buy one of the KLX/Honda clone 160cc hybrids that can be built up over 180cc. That would make for an interesting C70...
Personally I prefer the autoclutch for the basic 125 motors, though. Simpler (no clutch cable or lever to mess with) and especially on a Passport it greatly speeds up the conversion. Hanging a clutch lever on a stock Passport is going to require some fab work with the stock bars. Unless you're going to drag race or whatever I think you'll find the autoclutch is the way to go.
I'd rather have the "complication" of an oil cooler (two lines and an adapter plate) if I had a choice. Especially in hot weather this is a good thing.
Good to hear you've already got a 12v. bike. I'd like to find a good one and do a big motor conversion on it, making it look as stock as possible. Unfortunately most of the junquers I come across are 6v. models.