How fast do you want to go? Roller Cam? At 3000 lbs, Look for a cam between 265˚-275˚ max at .050 on the intake and 6˚-10˚ more on the exhaust. Eagle and Scat are OK on a budget although Callies is better if you can swing it, make sure you check all the clearances and have enough. .0028-.0033 on the rods and .0030-.0035 on the mains will keep you safe, you will burn up bearings from insufficient clearance long before you do from a little too much. Most cranks tend to be cut for 6" rods but at your weight it will run a little quicker with the 5.7" rods.
As far as heads, there is a lot of choices these days, Dart, AFR, RHS and Profiler all have some great stuff. If you plan to run standard roller rockers, not shafts, RESEARCH THOROUGHLY!!! A 420 will stand a lot of head, depending on the RPM range you want to run it in the 23˚ heads can flow well, but as they get bigger usually they require shaft rockers, sometimes offset lifters, and even raised runner intakes. When you get to that point, it's almost better to go with an 18˚-15˚ head.
Any more info on your expectations will help narrow things down a bit.