I know people do it, but I towed a small boat & trailer behind a Dart (225" slant 6, 145 hp) and it was misery unless the road was downhill.
There is no conventional speed equipment that will add 50 hp (my opinion: minimum).
The most practical is probably a turbo (eBay: Chinese turbo from On3 for $500 new) since the engine can remain completely stock except for ignition timing and the oil lines. Only works when you put your foot down.
