Sportfire sleeper

[Old sled guy]

So just looking for opinions/options for the most power that can be stuffed into a sportfire I have always wanted to make a sleeper sled and now is a better time than ever I am open to any engine options as long as they will fit under the hood (with pipes) i really want it to look normal from the outside to surprise my friends with new sleds
When i am not left in the dust for once. no ideas are bad-thanks

[Old sled guy]

Oh forgot to mention that the original engine was fried beyond repair (reason for all the fuss)

[Matt]

As far as bolt-on goes - you can install a front sub-frame from a Liquifire onto a Sportfire tunnel. Then you have choices of a Liquifire engine, or a T7 fan engine from an Invader that you can mod out and get AAEN pipes.
All depends how much custom work you can/want to do. If you can build/customize a sub-frame up front you can build one around an engine. Triples have been put into Liquifire frames more then once but it involves cutting and welding. If you want a liquid engine you will have to cut and plumb in coolers.

[Old sled guy]

yeah i was actually just looking at it today and measured the inside of it with the hood closed
It is actually bigger than I thought so I can probably fit a Rotax 500-521 but I know that stock pipes wouldn't fit because of height problems has anyone ever lowered a belly pan before on one of these or I could make a custom pipe from scratch

-side note i am not looking for bolt on at all more looking for a way to make the most hp i could fit in a small frame i am also making a skid from scratch to fit a track with taller lug while still looking original also no building welding or fabrication is out of limits -thanks for the ideas