The heater inlet/outlet hoses are different sizes - 5/8" and 11/16" on my '97.
I purchased a short length of each size hose and joined them with a brass adapter (red arrow).
Bypass hose is routed around the air intake tube (to avoid kinks) and reconnects below (yellow arrow).
Note - original heater hoses are still in this pic, just not connected.
Ran like this for 6 months till I replaced the heater core.
Alternatively, you could disconnect the stock heater hoses at the firewall and join them with an adapter - I was having difficulty disconnecting the hoses at the firewall, so made up this bypass..