As for the brackets....get
these (2nd product down) and you wont have to worry about getting the 89+ crossmember. Not sure if you have it, but you'll need the turbo 7M transmission (R154). The nonturbo transmission (W58) wont last too long.
Here's the bell housing for the turbo tranny to connect it to the engine. You'll also need to extend the harness on the dash side by about 18" As for a place to get it, I'd say a clip from
jarcoinc.com Look for JZA70 Supra. If you get a clip and it doesn't come with it, you'll have to buy a R154 driveshaft and support.