Yes, bike will keep the trans as it is part of the engine block. If I get lots of $$ they do make a 3sp conversion for the busa, that has a lot stronger gears and keeps 1st and 2nd gear ratio the same. Don't remember what third is.
1st gear will deliver the most hp/tq to the truck transmission.
170hp x 2.6 1st gear =442 hp going to the truck transmission (th350) in my case.
105tq x 2.6 = 273 ftlb
Second gear is a 1.9 ratio so the torque multiplication wouldn't be as strong, but would be capable of higher speeds.
Most of the bike engine buggys use a manual trans, and either the bike clutch, or fit an automotive clutch.
I'm not going to be negitive , I love to see this stuff on the trail.. But you are going to loose the torque that you do have in the converter and trans loss.
Then what little you have left in the 205. I guessing tons?? you may consider smaller more efficient trans, t-case. and front and rear. If not I hope your combo works.. love the weepow... look forward to riding with you on the trails !!!
I plan on using an automatic, just for the low rpm tq multiplication, slow speed crawling, don't have to worry bout it stalling all the time, or lugging the engine way down.
Playing with gear ratio calculator, I got 19mph, 27mph 45mph with the bike in first gear, th 350, np205, 5.12 axle gears and 35" tires.