The Lunarti kit is really afordable. I wouldn't use a set of different lifters. I also wouldn't use used lifters with a new cam. I run the 513/533 and love the cam. Car is like night and day. Ton of torque and low end power. Pulls hard to 6200 RPM. Very tame idle, plenty of vac for power brakes. The 513/533 likes a bit more stall then you mentioned and at least an 800 CFM carb. But i think the 603 would work well with your set up as it is. Summit has a good price on the cam and lifter package.