Which Stall?
Now, between those two options I would go SS3600. The SS4000 has a very high shift extension. When you factor in the rpm's you will be turning both pre and post cam, there flat out cannot be enough wiggle room for a 150 shot IMO. You would just more than likely blow through the converter. If you were staying N/A and wanted the most performance possible I would then say SS4000 over the SS3600.
Yes, you will see guys always wishing they went bigger with the stall but don't kid yourself a 3600 is no slouch. That's a large converter for a stock car and would be awesome with the cc503 you mentioned. I ran that exact combo myself, was going to spray a 150 shot through it but decided on adding heads and a PT4000 instead.
If you stick to a nitrous but change the heads and cam, you will most likely need to tighten it since the extra power will make the stall act bigger. If you go NA, you will need to loosen it a lot or even switch to a PT series Yank.
It will be quicker bolt-on NA. It will be quicker bolt-on +150. It will be quicker CC503+150. It will be only slightly slower CC503 NA at the strip, but just as quick on the street.
SS4000 will suck driving on the street with the stock cam, and will still be much worse than the SS3600 with CC503 on the street.


