In early 80's installed a Doug Nash in our 71 Vette powered by a destroked 400/.60 over bore small block. Car has a 3:36 rear gear and with Doug Nash low gear of 3:23 or thereabouts, gave me a 5:13 out of the hole. 5th gear on the Doug Nash was straight thru, no OD.
Car thru the Sanderson header exhaust/muffler and 28 inch street cars dial in was 12.5's at 111 to 113 mph as I recall.
Would full throttle shift at 6,500 rpm, missed a third gear shift only once, never ever broke anything. Car and transmission 35 years later still performs very well. Couple of years ago, pulled out its L-88 leg buster clutch and put in a nice comfortable Sach's clutch.
In the Vette was a total 100 percent bolt in except for a re-designed rear mount. Was one of the best buys in cars I ever made.