A Few Questions

Well, you don't have to worry about the intake! On the street, you definitely want a dual plane and the LD340 is one of the best ones.

Milling the heads would be the easiest way to up compression. With OEM pistons, you have less than is advertised. But then you may get into lifter preload issues. It can be a little difficult, but adjustable rockers & pushrods, which will likely have closer to the advertised 1.5-1 ratio, will compensate and help lift a bit. You will have to get shorter pushrods (About 7.23") to use with your hydraulic lifters. 273's with adj. rockers all had solid lifters with longer pushrods.

Very mild porting, focusing on opening up the valve pockets would be most cost effective.

A vacuum secondary Holley 750 (3310) may be easier to tune and provide a little more airflow. A 4-hole spacer wouldn't hurt.

You shouldn't go too wild on the cam with a conservative gear and converter. The low compression you're stuck with is another reason.

A 904 trans built to the same level as a 727 with the same spec converter is about .15 faster in the 1/4 mile. A good valve body or shift kit will help either trans live with OEM pieces. Aux. cooler is a good idea.

Nail head valves will flow a little more on the intakes than the OEM tulip-style.
The stainless replacements usually have less of a "pocket" on the chamber side which will help compression a tiny bit.