I'd say the V8 would be fine for 2wd stock wheels, no major towing.
I think it's a good looking van. Since the reserve wasn't met and they lowered it you might just call up the dealership and find out what the reserve is, or what there lot price would be if it doesn't sell, etc.
The only price info I know of is on SMB's website itself- look over all the sold and selling vans and go through the price sheets and see what having a new SMB built to the exact specs would be.
You can also use kelly blue book (kbb.com) or edmunds.com to see what the depreciation on an 04 with 76K is- it will give you an idea of chassis depreciation.
How you add and compare all those numbers becomes soft math
Consider how much you want/need an SMB now and what else is available as an alternative. Personally I've seen vans come and go after buying mine used and I'm still very happy I bought the van I did (right engine, right configuration, right 4x package, my wife likes it etc)