Big Block/A-518

Guitar is right, if the interface has 3 pins then it's a lock-up. Mine is a 93 and a LU. Here are some pics of what I've done...
Wish I had shaved off just a LIIIIITTLE bit more on the left side... but it fits. Make sure your pinion and output shaft centerlines are parallel, within 1/2*. My pinion is 4* up, my powertrain CL is 4-1/2* down.
Your speedo cable might need to be longer...
Also, I would recommend following what PATC recommends for having it shift automatically. I'm adding a rocker switch to act as an 'AOD OFF' switch, once I have more I'll post here.
Look around. A good friend of mine recomended someone who rebuilds trannies and motors/builds race cars on the side...He knocked off $100 because of it, but I paid $425 for my rebuild, case was acid bathed and my shift kit was installed as well. I waited 2 weeks, and backs it for a year if you keep your invoice.