Hi Ben, I would go for a stock Gen 5.5 5 port with 2072 pipe in the truggy Yeah I know, that sounds sort of backwards eh.
The Stage 5 5 ports are modified mainly for use in the buggy. They have more power across the board, but are timed for a softer bottom end so you don't flip your buggy over backwards , plus extended top end like a 7 Port. With these changes they are nasty in a buggy, but for sheer bottom end pull in a truggy the stock motor is probably better. Mark at Massive Mods may well be able to tweak you a Stage 5 5 Port with all the power and the full bottom end too - if so, go for it big time, as the 5 Ports are a superb motor.
As a bye line - The new Gen 6 6 Port (which is basically a highly modded 5 Port and a bit more) will hit the tracks soon. HP specs like you would not believe (dyno tested just the other day with 2072 pipe - x.x hp at the wheels) I won't give the figures out in case Mark's keeping it a secret for a little longer, but let me tell you it's higher than your probably thinking It is some motor.