I have a 1963 Sedan. I have been busting my butt in this car for the past 7years, only to discover that the puny 1200cc won't get me safely over the highway overpasses here in Houston. The overpasses are too steep for my little engine and every time that I get on the freeway, its a revisit to the "little engine That could" "I think I can, I think I can" Well, my heart has had about enough of such daredevil driving and would like to move up to a bigger engine. I live only four hours away from Mexico and I have been thinking of buying a fresh new bettle motor along with the tranny, but I am wondering if there were any differences in the pans from the 60's to the 70's that might make such switch impossible. Both pan and body are the original with the help of alot of aftermarket replacement sheetmetal.

I do know you can put a 1600 into a '63 without much difficulty. I'm less sure of how the later model Mexican swing axle tranny would fit. You might have to switch the axles & housings, but it's probably worth trying.

yes, you can put in a 1600 with no problem at all. if you do plan on putting a swing axle in it though, there is heavy modifying to do. leave the stock tranny and put the 1600 in, you'll be pleased with it.

The swap will work however, you have to use the fly wheel off of the 1200 as the 1600 fly wheel is to big and will rub in your bell housing. Been there done that!!!

you should convert it to 12 volt right away

Oh yeah...you're going to have to replace all the light bulbs and get a voltage reducer for your 6 volt radio. The 6 volt starter would probably still work okay on 12 volts unless you crank a l-o-n-g time. Does a 6 volt horn work with 12 volts? Maybe it'll go from a beep beep to a BEEP BEEP ! You'll also have to re-rig the heater to operate. The 1200 had doors that blocked the air exiting out the bottom. The 1600 had flapper valves on both exhaust manifolds. Getting the heater to function will probably be the big hassle.