L33 with L92 heads
 

Searched and didn't come up with the info I was looking for, sorry if I missed something.

I'm looking to do the cheapest LSx I can while still making ~450whp. The car is going to be road raced, so I'm planning on the Improved Touring baffle along with an Accusump, hopefully it will be enough.

My questions are:
Will the L92 heads bolt onto the 5.3? Any machining that needs to be done?
What about valve clearance, will I have an issue with that?
How do I deal with the oil drainback issues these motors have? The last LS motor I raced had WCCH L92 heads on it and I could never fix the drainback issue. I have seen that people drill the lifter buckets, does this actually fix it?
Any suggestions on keeping budget down while obtaining about 450whp? Must be an aluminum block.

edit: Also, I can get a 6.0L L76 from an 2007 silverado for pretty cheap. Is this a good starting point? Could I use a standard LS1 wiring harness/ecu?

5.3 bore = 3.78"
Minimum bore for L92 heads = 4.00"

If the valves even cleared the cylinder wall, they would be horribly shrouded. Since you have a line on a 6.0L, that would be your best route. More displacement makes it easier to reach your goal with a milder cam (less rpm, more reliable, etc.).

a 2007 truck wont have a l76. it can have a 6.2 l92, or an iron block lq4/lq9 6.0. definitly find out if its the 6.2, since thats your best option. Also, i would shy away from the 5.3 block, since you are road racing, and unless your displacment affects min. weight, bigger displacement always makes for an easier car to drive.