In my quest for the better mousetrap, I am going to make a offset drive from my gearbox output down and across to the centre of the car, as my prop shaft comes out just where I need to put my pedals. Reading a recent post on here, It raised the question about chain life,

http://www.locostbuilders.co.uk/forum/23/viewthread.php?tid=189975

I have 2 options, use a 50mm x 8mm pitch belt, which does take up quite a bit of space, ------, needs to be quite rigidly mounted so the belt runs flat, any more than 1deg parallel runout and the belt life and strength is compromised, but the advantages are I have a built in cush drive if I use a sprung tensioner, Surprisingly, I can mount the pulleys on a 25mm keyed shaft using taperlocks, which are well within the torque/weight loadings I expect to put thru them,
Or use the bike chain, 18t sprockets, and a total length of chain of about 500mm,-- this will entail making custom sprockets and bearing carriers, my worry is the chain and sprocket life, I don't know how long the chain last or for that matter the sprockets either, I don't want to be making custom sprockets every 2k

Do they have to be 18T sprockets? The bigger the sprocket the better the chain life.

If you can mostly enclose the chain and provide a total loss lubrication (e.g. like the Scottoiler system used on bikes) then chain life should be pretty good. If it's exposed to loads of crap from the road and it's difficult to access for cleaning etc. then not so much.