Good morning everyone. I'm new to the forum world and new to Mustangs. I recently purchased a 66 coupe for my wife's 40th birthday. The car was in pretty good shape overall. I had it painted, new interior, and tuned up, etc. I've been having a few issues with it running a little rough, hard starts, etc. I have replaced the plugs, wires, coil, rebuilt carb, new points, etc. The more I've researched and messed around with the car, the more I'm finding out it may be a Frankenstein car. Here's my biggest question. The block stamping is C5DE 6015F. To me this designates a 65 Falcon motor but is it a 170 or 200? It has 3 freeze plugs but the research I've dive says that early 200's had the 3 freeze plugs. So I found a tag on the coil bracket and after rubbing the paint off, it says 170 64 4F which indicates a 1964 170 ci motor. I know people swap things around in cars, and honestly I don't care which it is, but I'd like to rebuild it and the 3spd auto tranny. Any thoughts, suggestions, help? I just want to know which motor it actually is. Also, the carb does not look like any I've seen that should be on this car. It's a 1 barrel, supposed to be an scv but it only has an accelerator pump on the drivers side. No pump or other valve on passenger side. Please help!