Check your flexplate bolt pattern(s). Some have multiple, and others are drilled for a specific TC. Otherwise, it will work.
It will probably stall higher with the 455 because of the additional torque. As a guess a flash of around 2400-2600+RPM's.
Yes in most cases, THM350 and 400 converters will fit providing the flexplate has the right bolt pattern, most are drilled for both. As mentioned, it will stall higher behind more torque and in a heavier car. Actually, you can’t know where it will stall until you install it and road test the car. Off the shelf or used converters are a gamble IMO. You usually get what you pay for.
thanks for the info. my tranny guy was suppose to do 2200 for the turbo 400 but when i got it home is says th350, and i am not sure how it would work with th 400. i guess make the call to the tranny shop and tell them the mistake.
It has nothing to do with the transmissions. The converters will fit onto either transmission. You can take a converter that was on a THM350 and it will fit and function on a THM400. The fact that yours is labeled THM350 is irrelevant. How high or low it stall depends on several factors, engine torque, car weight, gearing etc.