You are going to run into a problem , because the th4 is about 5 or so inches longer than the dynaflo,,,, take a look at the frame and rear mount on a 64/65 riv.... to see how Buick did it and do the same thing.... You will have to change the front yolk because the th4 yolk is a different size and different spline count,,,, and shorten the front drive shaft to accomodate the changes.... you will need the services of a driveshaft shop....with the 63 crank , you will have to have a th4 flex plate that has had the center hole opened up by a machine shop enough to slip over the flange that is on the back of the 63 crank... I did this and never had a problem even racing the engine hard for 3 years.... you will also have to have a ''short nose'' starter to work with the th4 flex plate....
Your shifter should work with some adjustment.... in fact the shaft that bolts to the shifter yolk will just bolt up , if I remember right,,,, you may have to lengthen the shifter rod some.... the vac modulater will have to have a pipe run to its location and hooked to the intake .... the tube for the dipstick will just bolt up.... but the lines for the trans cooler will have different fittings so you will have to change them out and route the lines to them.... as you can see it aint just a bolt in,,,,, but it is well worth the effort especially if the new trans is a switch pitch.... they put a lot more power to the ground,,, and yours is a switch pitch....
