AC does, in fact, offer better regen ability, but is fairly expensive. You're looking at > 10k for a decent motor/inverter combo. You can do regen with some DC, like sepex motors. Regen is not my forte so I'll let someone else comment further.
100 miles for a heavy vehicle will be extremely difficult to do on any sort of budget. Figuring something large, like 500 wh/mi when loaded, you're looking at 500 wh/mi x 100 mi = 50,000 kwh. At a DC voltage of 156 (one of the largest DC voltages commonly used), you're looking at 320 Ah batteries. I can't find anything in this range, so you're looking at making a large pack larger by putting it in parallel. Even using something cheap like FLA, you're looking at ~ $300 per 150 ah battery, and to get 156v you need 13 of them. Multiple by 2 to put them in parallel and you get 26 $300 batteries for about ~$7.8k. And, these weight about 100 lbs each, meaning you just put in 2,600 lbs of batteries, meaning you probably don't have the weight left over to put anything in the truck.
You can overcome the weight with Lithium batteries, but then your price goes up dramatically. You're talking ~ $1.20 per Ah, so $360 per battery (if they made 300 Ah lithium cells available, which I am not aware of right now. You're back to putting sets in parallel, but since the cost is per Ah, it doesn't really matter). However, these are only 3.4v each, so you'll need 45 of them. 45 x 360 = ~$16k. (this would probably be something more like 130 100 Ah cells but the price, again, is given per Ah so for our math it doesn't matter).
The 100 miles is really the sticking point. It is very hard to get 100 mi on a light car with what's available to DIYers. When you make it a 3,500 lbs vehicle, that just isn't realistic on anything short of a fantastic budget.
The axium is, you can have range, low cost, and speed. Pick two. If you were to run this like the space shuttle crawler, where it moves at .3 miles an hour, you could maybe do it on a budget, but it would be a lot of work still, and still very tough.
100 miles for a heavy vehicle will be extremely difficult to do on any sort of budget. Figuring something large, like 500 wh/mi when loaded, you're looking at 500 wh/mi x 100 mi = 50,000 kwh. At a DC voltage of 156 (one of the largest DC voltages commonly used), you're looking at 320 Ah batteries. I can't find anything in this range, so you're looking at making a large pack larger by putting it in parallel. Even using something cheap like FLA, you're looking at ~ $300 per 150 ah battery, and to get 156v you need 13 of them. Multiple by 2 to put them in parallel and you get 26 $300 batteries for about ~$7.8k. And, these weight about 100 lbs each, meaning you just put in 2,600 lbs of batteries, meaning you probably don't have the weight left over to put anything in the truck.
You can overcome the weight with Lithium batteries, but then your price goes up dramatically. You're talking ~ $1.20 per Ah, so $360 per battery (if they made 300 Ah lithium cells available, which I am not aware of right now. You're back to putting sets in parallel, but since the cost is per Ah, it doesn't really matter). However, these are only 3.4v each, so you'll need 45 of them. 45 x 360 = ~$16k. (this would probably be something more like 130 100 Ah cells but the price, again, is given per Ah so for our math it doesn't matter).
The 100 miles is really the sticking point. It is very hard to get 100 mi on a light car with what's available to DIYers. When you make it a 3,500 lbs vehicle, that just isn't realistic on anything short of a fantastic budget.
The axium is, you can have range, low cost, and speed. Pick two. If you were to run this like the space shuttle crawler, where it moves at .3 miles an hour, you could maybe do it on a budget, but it would be a lot of work still, and still very tough.