When installing the newer heater core with the 3 aluminum tubes already attached:

Once the console and heater control switchbox are removed or out of the way, would it be possible to install the heater core with 3 alu. tubes already attached? In other words, push the 3 tubes through their firewall grommet to mount the heater core.

This would be instead of installing the heater core, then trying to attach the 3 alu. tubes afterward, which by all accounts is a gross PITA.

From the RealOEM parts drawings, it looks like the 3 tubes pretty much go straight back from the heater core, penetrating the firewall perpendicularly. So, can you just install the HC+3 tubes as a unit?