3/4 hp is all you need .. now if you were doing head's and big stuff the bigger hp would be fine and as for production the machine is only as good as the person working it .. i run a 3/4 hp and not once have i bloged it down ... and i do intakes and heads with it .. i run the higher rpm and the lower rpm both with goor results ... if you are starting out start with the 3/4 and work your way up the bigger motor may be to much for you when you can get away with the smaller on .. i toss stacked 12 with not problem on a 3/4