Well, I am pretty happy with my tko600. After the intial break in period this trans has turned into a dream. Quiet as the stock trans after the break in. And the shifts are very smooth. Speed shifting into third will taking some learning because of the position of the trans. It sits about an inch closer to the passenger side inside the tunnel. But nevertheless its honestly no big deal.
The only big defferences are the gear ratios. And honestly I think the ability to handle an extra 100 fy/lbs isn't that important with the 600. Choose which one you want based on the ratios. 5th is .64 rather than the stock .68 that comes in the 500. And the 1st gear in the 600 is a 2.89 I believe rather than a 3.27 which comes in the 500 and t-5's. 1st is a little longer than stock but since you're probably going to be going back to a power adder, it would be nice to have an extra sec in 1st to pull you out of the hole. Are you going to a singe setup? I remember you scrapped the twin setup.
I have the driveshaft spacer needed for the swap in my dresser, if you want it just pay for shipping and its yours. You will also need 2 shorter bolts for the top two holes in the bellhousing. Obviously it would be a wise choice to index the bellhousing while you are down there. I didn't and havent had a problem. But paul had problems with his 3550 which he told us about when I had a thread goin about my problems gettin the trans it. (Ive never takin a trans out before so thats what my problem was.)
You will need to ditch the exhaust hanger bracket on the bottom of the trans.
Also, I remember reading that the way the trans mounts to the crossmember, it sits about a 1/2" lower than stock. I cant confirm this maybe someone else can chime in. This will throw off the pinion angle which will cause vibration. And I have that problem right now. But only at speeds 90-100 and above.
You will also need a 26t clutch disc and have the new yoke that comes with the trans installed on your driveshaft.
Thats about it. If I left out anything feel free to ask. Great trans in my opinion anyways. BTW you will also need a clutch cable dust cover from a 87-93 car. Our factory one doesn't work.
Dan.