Brand new to Thermoquads- a few questions I need help with

A TQ with 1 3/8 primaries will respond better on a smaller engine then 1 1/2.
I've been using a 6138 (72 340) TQ on my 318 with a whiplash cam for a few weeks, I originally had it on an Air gap intake with square bore to spread bore adapter after getting it adjusting the Air door and setting it to the longer stroke setting on the Accel pump it was running good. I have now went backwards and am running the same TQ on the 318 with a stock cast iron 340 intake manifold. Lost alot of low end power.
The main thing with running the TQ on a smaller engine is air flow, mine seemed to run better and had good low end power on the air gap manifold.

If your set on running a TQ on your 273 I would try getting one that was on a 318 and stay away from lean burn models and other emission component models.