I have a fair bit of experience with the Vortec heads. I would suggest using the springs that the cam manufacturer specs for your cam. The lift limit is only partly due to the springs, the valve guide bosses are quite tall, there fore you should check the seal to retainer clearance too. You should have .050" or more at max lift, if not a machine shop can cut the bosses down. I would also try to keep the compression down to about 9.0-1 or 9.5-1. 10.0-1 is alot for Iron heads and pump gas with a mild cam. These heads don't need much total timing, try around 32 degrees. You may also want to drill a small .125 - .187 hole in the thermostat. These heads block off the bypass port in the block. You don't have to do this but it doesn't hurt anything. These are the things I have learned running these heads on my 70 Nova street & strip car. All in all they are a good bang for the buck. Good luck.
Sean
