edelbrock carburetor secondarys

Ede's are notorious for the floats to be out of wack from the factory, so take the top off and make sure the floats are set correct.

As far as jets go,without an AF gauge,or dyno,it can be difficult to get it nuts on.
And with today's fuel,reading the plugs has become more difficult.
So without the above, it comes down to timmed runs or seat of the pants.
Trial and air all the way.

Having said that,I usually go up 2 sizes on my secondary jets, on my Ede's.
Seems to like it on the top end.
When playing with the springs, I always seem to go back to the Orange spring. It always seems to work the best. Again trial and air.

You are also dealing with a 4x4 truck, so your setup will be different from a street car. Off idle torque when wheeling is what you need. That 600 out of the box stock should work great for what your doing. That's where I would start (factory box stock), with the floats adjusted.

As far as a surge, I would lean more towards a vacuum leak.