Have fun. I put one in last year, non viper spec, just the ford racing version. Only a few mods.
There is a good chance your prochamber will not fit, as I think the prochamber part actually interferes with the relocated cross member (cross member has to be mounted about 3 1/2 inches back to mount the trans mount to). Take a pic of it with dimentions so I can see the location relationship.
Believe it or not, Summit sells a energy suspention poly trans mount for a t-56 into a fox body $30 or something. You have to call as it's not on thier site. I can get you the part number if you need it.
Driveshaft- this has been a challenge. I had a custom aluminium shaft made at 44 1/2", but would not fit, so I got another one at 44" and it works perfect. If you didn't buy the $400 one from D&D, let me know if you need one at 44 1/2". I believe stock is 45 1/2". $100 and it's yours.
No need to modify the trans tunnel, or cut the shifter opening.
Not sure about the gear ratio of the viperspec, but mine is mated to a 3.73, and I can tell you that I hit 140mph in about 10sec, at 7k rpm, and just shift into 5th, not to mention 6th.
Don't forget to get the cobra silver and leather 6 speed shifter knob for $30 too. lol