Your doing pretty good for pump gas. For the HP your looking for your going to need a .525 to .550 lift and about 250 duration at .050. Need a single plane intake like the victor jr or Team G. Ditch the edelbrock carb and get a holley 750HP series or so. I picked up a new Holley 835 cfm HP series carb last week on EBAY for $300!!! Headers in the z, I have the full length headers from S&S, not the best, but better than the restrictive block huggers. Get you a underdrive crank pulley, like from moroso, that'll pick up a few rwhp as well. If your running an auto you'll need a 3K stall to make that idle in gear.
Yes, you will have to get different pushrods but you need to check it when you go changing things. Rule of thumb is, the more you go trick parts, the more you have to check things to make sure they are aligned right.
So, if you buy all of that cam, lifters, springs, pushrods, carb, headers, etc, etc, you could probably sell the heads you've got and get some AFR 195 eliminators, might be the 205's I can't remember. Which is why we typically beat the band wagon on cylinder heads, get cylinder heads and the combination you have will make what you want, no other changes necessary, well except maybe the headers. I'd ditch the carb for sure, but if you get heads you'll be making 430HP or so at the crank!