Might not be a bad set of towing twins. Forget about the 66 by itself for towing. Personally, I like the hx35 over a s475 or a ht3b. You can get a new s475 for about half the price of a used bullet... Sell the 66 and buy a 475.
35 over a bullet wouldn't be a bad 500hp setup for towing. Actually, it would probably be great provided you aren't spinning it over 3500RPM or so.
If you have them, go for it. Watch the drive pressure, and tune it so the drive pressures stay in check....don't worry about boost as much. Everyone gets hung up on making a lot of boost....air in, air out....period!
Chris