Got a 2 litre Carlton based trike that occasionally gets the sphincter going if you start "over egging" the mixture.
Haven't got a clue what it will do flat out or what it's 0-60 times are, but I estimate the power to weight ratio to be around 200 BHP per tonne so there isn't much out there that will keep up with it off the line (or rolling acceleration come to that).
Bought a scrap car with good running gear, obtained a headstock from a rather large motorcycle and had a friend build a box section chassis around it, then simply dropped the running gear in to place. It took 3 months, 100's of litres of homebrew, and quite a few favours to build from start to finish with the final cost of the project being just under £1000.
It's not pretty and it's not really practical for everyday use, but it provides an awesome grin factor and gets you noticed immediately wherever you go. It also has the added bonus of being quite cheap to run with road tax costing £66 per annum, insurance (fully comp with agreed value of £3,500) is £112 for myself with the missus as a named driver, and an average MPG that will remain in the high 30's around town providing you don't go mental with the right hand.
I dropped a crashed(wheel had fallen off due to wrong wheel nuts) Mini based trike off at a customer's house back in the summer, and his own trike used a Senator engine. He reckoned that it was 'comfortable'!
My old boss had his dad build a trike, from bits and pieces in the yard, to keep the grumpy old git out of the way. A shaft drive Kawasaki and a Sierra IRS were the main bits, with a lot of work from Brian who was a good engineer. The grand unveiling was impressive, as neither of them had realised that the bike engine turned the wrong way. So, Simon let the clutch out to find himself heading backwards on this hugely unwieldy thing, with the rest of us, who had 'forgotten' to mention the problem pissing ourselves.