Single pattern wide lsa cam with vortec heads?

[F-BIRD'88]

With a these cams in your 350 vortec motor including your summit 234-234 cam
you will want to recurve the distributor advance curve.
Shorten/limit the mechanical advance stop limit to 10deg ( 20 is stock)

Now this allows you to set the intital idle base timing to 26deg BTDC

26deg at idle.... 36deg at max mechanicial advance. Then use 2 advance springs that bring in the full mech advance around 3000 rpm yet work smooth.

Then plug the vacuum advance into ported vac on the carb.

You cannot get the desired advance curve just by swapping adv springs in the diz.
You need to set the mech advance limit stop to 10deg. Easy on a GM HEI diz.

26 deg initial base +10deg mech adv ='s 36deg total

Enjoy. Post a vid of you smokin the tires...ha ha