Switching Engines

["Elon" <saltfever@comcast.net>]

How does one register and pay fees if you want to run TO with one engine and
then switch engines and classes?  I would like to consider a mule motor for
licensing runs, car check-out, and set-up; then switch to a serious motor.
Do you have to pay two entry fees, or can you just register for the "class"
engine, but run TO on the mule engine.  Is there a separate tech inspection
for both engines?   -Elon