Does anyone have a good (cheap) online source for radiator hose? I've read on here the "green stripe" hose is good for under the car. Would that be made by Gates? Does anyone have a rough idea how many feet I will need for my SBC install?

Yes Gates makes the green strip, a very rugged hose. Just do an internet search for gates green stripe hose.

West Marine often has it in stock, and many hot rod shops also sell it I am sure it can be mail ordered too.

the length all depends on exactly how you route it, then you may want formed elbows and such in the engine bay and trunk to make hook up easy as it is difficult to make a tight bend with it. You really need to get a rough measurement under the car in the way you route it. Besure to buy a bit extra, better to have to much than be short a bit and have to make an extra splice.

Napa has their own version of that type of hose. West marine would be sure to have some though, probably even gates if I remember correctly. Heavy and expensive to ship. Semi-Truck garages would have it too

I'll go measure what I have in a bit and get back to you. I'm doing homework and plan on tinkering in the garage in about an hour.

What diameter is it?

I'm sourcing a radiator now. Looks like the inlet might be 1 3/4" and the outlet 1 1/2"