There were more Simplex bikes there than anything but the Cushmans. Not very many guys had one...there were gobs of em everywhere and on trucks or trailers.  Seems they're all being found and dragged out.
  I've struggled with if few things of late or I woulda thrown he truck together. Next year I guess.

Those TAV clutches don't really care what driven pulley you choose...I believe a stock TAV30 is 6" . They make. 7". 
It won't suffer at all because the take off is geared really low( look at it bouncing off the brass bushing, it pretty small when the pulley grabs it)..as it works it actually goes to an overdrive...big in front and small at driven pulley.
They're really smooth and effective. Low end grunt isn't a problem.

Carryall....where did that fishtail come from?

I see now, was wondering,that's all.    Keep building

I'm counting 6 sprockets...pedal power 2.   Engine to jack shaft 2 then 2 drives.  Can't you just come out of the 5 sp direct to rear? Why go to the shaft?

One more pic

Well,the lawn mower differential would allow the slippage on corners ...but we shall see

The trucks at a standstill but I've gathered some stuff for it .I know I keep saying soon but things come up.
 The engine choice is kinda tough when I look at starting and charging systems. On the one hand harbor freight is easy,cept it doesn't charge...and that TAV requires a seperate bigger driven unit than it comes with and two clutches(like ricks)..looked at the differential axle from northern tool....it'll need a seperate clutch ahead of it adding another belt which I think will look cluttered...then there's the whizzer engine..electric start is doable...and then your right back at how to clutch it.
  I'll get to it before summers end though.