500 cfm edelbrock carburetor...

Your slant will run fine with an Eddy 500.
I ran one on a stock slant with the same Clifford intake/headers.
Took it out of the box,adjusted the A/F and idle and away I went.
Just a little understanding an tweaking is all thats necessary
For starters,make sure the floats are set correct.
Blow out all jets and passages with compressed air to make sure nothing is blocked.
Slap it on.
Make sure the A/F screws are set correct at idle.
Make sure you have the optimum timming setting.
If you think your rich in cruise mode,do a simple rod change. (couple sizes bigger).
You can also adjust the pump shot,on the arm.
With the vacuum secondarys,youll be fine at WOT.
We havent seen the rest of your car,so we dont know that it is running rough because of the carb.I will take your word that everything else is up to par.
With a little understanding of how the carb works,and a little tweaking,it will be fine.