Honestly I have not read too many good things about the truckzilla conversion. Take other people's opinions than mine but I would pop for another picco before I'd go truckzilla.
if you read up on the savage forums, you can see all of the problems that individuals have had with motor problems. Save your pennies for the RB concept .28, it will rule All!
I had put the picco 26 in my savage before I did the zilla conversion. The zilla is a little bit faster because it is geared higher for topend speed. However alot of people have been having problems tuning the HB 46 engine and the picco 26. The picco 26 needle valves are kind of tricky to set just right, the engine want to bog down in mid range patience and a steady hand can eventually get the proper tune. When I got my truckzilla motor the first thing I did was to take the motor apart and inspect it for foreign material like metal shavings, which it did have . I cleaned it out lubed it and put it back togather and I have not had any problems with the 46.What really concerns me is HB poor customer service record so far. I think they got caught with their pants down , the demand for this kit surpassed their expectations and they don't have enough replacment parts on hand to meet the demand!! I hope they correct this soon. You can't race it if there are no replacment parts on hand. Get a picco now to bash around with and if hot bodies gets their problems worked out and you still want a zilla go for it. I like my zilla
If you gear the truckzilla low it becomes a wheelie monster so the advantage would go to the picco 26 . If you gear it tall the truckzilla would have the advantage for more topend speed because of the extra torque and large tires which actually alter the final gear ratio for the zilla.