Do you mean straight live axle as in a gocart ? You need a differential to allow for cornering .
If you mean straight instead of independant , thats fine . most of them use an automotive axle from smaller rear drive cars . a lot of times they need to be shortend on one side at least for driveshaft alignment .
There are several trike builds documented here in the Technical forums . Look at the top section , in the "stickies"
Thanks everyone. The Honda Interstate I have doesn't use any oil at 95k and I hate to part with her but I do realize a reverse gear is good to have. Been looking in auto salvage yards for a ranger or mustang rear end. Thanks everyone for the info.
The only sound I hear while riding my wing is the sound of air being sucked in behind me. What a ride!