New to this site and reading tons of past posts ; just trolling the threads , learning as I go . My V6 engine swap into my 55 Chevy is my way of cleaning up the shop , using all the pieces that have been lying around gathering dust for ages . My old Chevy sat in a barn waiting for me to retire for 23 years , and finally got dragged on home for a resto-mod . I had a neighbour unable to sell his rusty 95 Astro with a new V6 engine and 4L60E trans , so finally took pity on him , brought the Astro home and stripped out engine, trans and the ECM and harness . I scrapped it , and sold the trans and van body for what I had in it . Hiding under the bench was an old M20 Muncie that needed a new cluster and bearings , so one thing leading to another , I put the engine and Muncie together with a new clutch , and stuffed the powertrain in my 55 Chevy . I now have a shop full of wire harness to sort out , then bought the GM Astro manuals and am sorting out the wire harness one sensor at a time . I ran into a small snag with the VSS input for my ECm , and (finally) that brings me to my question of the day . I unwrapped the ECM out of its box , flipped it over to get part # for further research , and discovered 2 part #'s , one above the other , the top #1619747 , and under that is #16212125 . My question is , which part# is for the ECM ? According to the manuals , there's no anti-theft (VATS) to worry about , and I'm using a 4-speed so the auto trans harness isn't needed; another question might be , do I need to worry about those missing trans inputs ? For the VSS signal . I'm fabbing a 40-tooth reluctor wheel onto the front yoke of the driveshaft ; i was going to build it into the case of the trans , but this way is more fun and less work . Your forum is amazing ; I had no idea the web would lead me here . The learning curve may be steep , but so was Pike's Peak and we did that in 1969 ; just love to learn new stuff. Be safe...Bob.