Touchy Valve Clearances & Compression

When I set the timing marks for making valve adjustments, should the alignment mark be right over the "T" or can it be anywhere between the "T" and the "F"? Can this make a difference in compression? I've been putting it directly over the "T", or as close as possible.

Perfect factory compression should be 156 PSI for a 1981 KZ440 LTD. After doing a top-end rebuild of the engine, the compression in the left cylinder is about 135 PSI and the compression in the right cylinder is about 120 PSI. I have found that I can tweak these numbers quite a bit by adjusting the valve clearances. I got the left one up to 145 PSI, but the right was still about 125 PSI. It seems like I am chasing my tail trying to get these number a little better. Ideally both cylinders should be about 150 PSI, but I'll take two cylinders at 130 as opposed to one at 145 and the other at 120. Any help you can give me to get me there would be appreciated.

As long as you have sufficient valve clearance (like .003" or more) additional clearance should NOT affect compression. I would carefully check valve timing.

If the 440 is like the 750 twin, you check valve clearance when the cam lobe is pointing 180 degrees away from the lifter. Has nothing to do with ignition timing.

The 440 Is a sohc rockerarm design, so you do use ignition timing marks to set the valve clearances.
Set the valves to factory specs and check compression. If it is low do a leakdown test and go from there.