Turbo transmission won't be necessary unless you are going to put in something monster-sized like 11" or greater. As you mentioned, it really boosts the price.
As usual, before you convert it, make sure the 12v system works perfectly - you wont' want to debug it later.
Also make sure the body is in good shape, as you won't want to fix paint / cosmetic issues later.
Top speed of 90 is doable, since you are keeping the transmission.
To get 0-60 of 6-7 seconds, you're going to need a rather strong motor - perhaps the Warp11. I don't think the Warp9 will do it (but I could be wrong).
To get 80 miles, let's do some math:
Assumption: 300 wh/mile.
80 mi * 300 wh/mi = 24000 wh = 24kw.
That is how much usable energy you need. However, you can't use the entire battery without damaging it. So what you need is at least this:
24kw = pack * 0.8. Pack = 24kw / 0.8 = 30kw.
Depending on your controller, that will determine the pack voltage and from that, the pack Ah.
Example: 120v pack, 250Ah. I'm not aware of any 250Ah batteries tho - so you'll need to a different size: 200Ah (for less range) or pairing 130Ah batteries to get 260Ah.