I'm going to be Buying a Tremec 500 here soon
Just got the insurance claim and sold the Bimmer

Will it mount up to the stock t-5 bell housing
I plan on gettin a new crossmember to relocate the torque arm to the crossmember
So I'm getting another crossmember
But will my stock bell housing work
Will by stock bellhousong link to a pre 85 350 since I'll be getting a crate engine as well.

Call Bob Hanlon @ Hanlon motorsports.

I think an adapter plate is used for case to bell fitment.
Good call on the torque arm re-lo.
84-92 T5 bellhousings are all the same. The change in 1986 was at the crank / flywheel bolt pattern and flywheel balance.
I'd get an 87-up for easy roller-cam fitment and the 1-piece rear main seal (fewer leaks; easier T56 swaps.)

So a plate is used from the Tremac case to the t-5 tranny

If all 84-92 bells are the same I assume I would just need a different flywheel.

Also I'm thinks of buying an 83 with a 5 speed
Would that be the same bellhousing
Since you specified 84/92
Cause my car is auto and I need to convert
I would rather buy a running car I can drive then switch when time comes
Would I be able to swap in a 73-85 350 crate engine and have the stock Bell work.
I also know 83 is mechanical linkage over Hydraulic that does note bother me
But would that mean they use a different bell on the hydraulic systems.

Or should I just go the T-56 route

If you can afford it, go T56. That way you wont have to worry about grenading the T5 if you put any decent power to it.

Since I have to convert to a stick I need all

The manual pieces
Pedal, slave and master, crossmember, bellhousing
You know everything
A brand new TKO 500 is $2200
Plus everything else
I highly doubt a t-56 with around 100k is that much probable that's much with a bell and a few other pieces so that why I asked about the tremac TKO linkin up to the stock system vs a t-56
Cause if I can find a totaled 3rd gen that's a stick I'll just switch the whole car over and look to a TKO 500
But we shall see

Or any ideas on what a rebuild on a t-5 would be so it could handle a mild day. 400-425 lbs of torque

You can rebuild the t5 with the gforce heavy duty case to make it live a bit longer for cheaper tha. A tko ot t56 swap. Not ever going to be as strong but unless your using slifks you wont have enough tracton to break it anyway

Heavy duty casing or Kit
A tranny casing or Tranny rebuilding kit
Dosent casing mean the housing the Gears are in
How would just changing the tranny casing make it heavier Duty
Wouldnt you want Heavier Duty gears
Or was that from a smart phone which usually makes us look not so smart cause of the auto spell crap

And did you mean as long as I'm not running slicks
What about Drag Radials?