Don't want to rain on your parade (agree with Mechman - it's a fun project - dive in!), but you need to manage your expectations.
I predict you're going to have a very hard time getting the range you want from the batteries you're being offered. To start, you're going to need to know the rated & actual (tested) capacity of the batteries you have access to.
My buddy & I paid scrap rate for the used golf cart 220Ah batteries in the ForkenSwift, and the best range they ever provided (about 3 years ago) was 35-40 km (20-25 mi) when driven extremely conservatively in ideal, warm weather, at a low average speed, probably below 40 km/h (25 mph).
With ForkenSwift, we would have been satisfied with a real world working range of 16 km. That's essentially a trip across town & back again.
