454 marine power heat exchanger replacement

I'm currently swapping the heat exchanger (frt mount) on a 454 marine power engine. The old exchanger had a 1/2" connection to the thermostat housing (bypass hose) while the new heat exchanger does not have this 1/2" connection. I am told that (but cannot confirm) that i should reroute this bypass hose from the thermostat housing to the water pump (remove existing fitting). Anyone run into this situation with changing the bypass hose between the thermostat housing andthe heat exchanger to the thermostat housing to the water pump? thanks (original exchanger pic attached)

Is this a 4" or 5"? is it freshwater cooled with raw water through HX and Risers? You should have had a one to one fit - all fittings the same. I just did this on one of my motors and was able to swap 1 for 1. For the record, I have not heard of rerouting the bypass.