Recently swapped the original TH400 for a 700R4 in my ‘74 Corvette using the Shiftworks shifter kit. Seems to work okay. Keep in mind that if you do this, you will lose the functionality of the transmission interlock cable coming from your steering column. The original bracket from the TH400 that mounts the end of the interlock cable to the transmission pan bolts will not match up to the bolt pattern on the 700R4, unless you can modify it to fit. I’m considering doing this myself.
Recently swapped the original TH400 for a 700R4 in my ‘74 Corvette using the Shiftworks shifter kit. Seems to work okay. Keep in mind that if you do this, you will lose the functionality of the transmission interlock cable coming from your steering column. The original bracket from the TH400 that mounts the end of the interlock cable to the transmission pan bolts will not match up to the bolt pattern on the 700R4, unless you can modify it to fit. I’m considering doing this myself.