853 heads on a 6.0...boost later on
A little port and chamber work and they can easily flow as well as a ported 243.
With the lq4 pistons, your compression will be around 9.4, 10:1 with lq9's.
With boost the higher compression will hurt you while the lower compression will hurt you n/a.
If your looking for only 500 at the wheels, I would do it with heads, cam and compression. Easily obtainable with a 6.0
If you use the 63cc 241's or similar, you will have around 10:1 with the dished pistons and higher with the flat tops.
There is really no combination of parts that works well n/a and with boost unless its a stock setup which your only planning 5 to 7 lbs and even then it's not optimal.



