Assuming you bought the version with the "smaller" springs......
For that cam with 1.5 rockers I would just adjust the installed height to get those springs to 145-150 on the seat(around 1.80-1.82 installed height).
The rate of that spring is fine for that type of cam if the seat pressure is set properly.

IMO, the 1.550 flat tappet/hyd roller spring they use is on the stiff side for most hot street or street/strip type applications.

In my original TF240 thread I'm pretty sure I posted the numbers for that spring....... It did not match the specs on the instruction sheet that came with the heads, but I seem to think it was pretty close to what TF shows for specs on their spring page.
It's been a while....... You'd have to do a search.

Depending on how high you want to turn the motor, what rockers, etc...... Something along the lines of a Comp 928 or Isky 8005a is what I'd be looking at, but both of those install shorter that how the 1.550 springs come set up from TF, so you'll have to play with shims/retainers/locks to get where you want.