New Heater Motor-Blown Fuses

[Short 3/4]

I recently replaced the original heater motor on my Thrift-Air 65 heater with a new one from the local parts store. I knew I should have been suspicious when they had one on the shelf. Fit right in, and boy does it blow a lot more air than before. Unfortunately after about a minute on high it blows the 10 amp fuse. Turns out the new motor draws just north of 15 amps. Obviously for a newer model truck, probably with AC. Now I know plenty would just pop in a 20 amp, or even wrap the old one in foil, but as an old electrician who spent a lot of his career as a troubleshooter, I know that won't end well. Figure I have a few options:

-Never use high. Hard to do now that I have that ultra high speed it never had before.
-Rip out the new motor and try to find the right one. Again, giving up that new high speed.
-Put in a relay. I hate the thought of cutting up my brand new under-dash harness.

Any other ideas? I can't be the only one out there with this problem, what have others done?

Appreciate any help,
Tom