Well, he built the engine and doesn't want to push it. When you dyno test an engine, you should keep advancing the timing until no more gains are measured.
The things that cause an engine to need more total ignition timing are the following:
1) big bore (long way for the flame to travel)
2) domes or dished pistons (makes the flame travel around uneven terrain)
3) inefficient combustion chambers (makes the flame travel slow)
A BBC with old style cylinder heads and domes will have all these issues. This is why BBC typically are less toleration to high compression as compared to SBC are most other engines.
I have seen dynos of old bbc requiring up to 42 degrees of total timing to make max power. My 454 runs best with 40.
I think your compression maybe lower than 10.5:1.
9cc head gasket (0.039" thick felpro)
4cc piston below deck
(899-29+120+9+4)/(-29+120+9+4)= (899+104)/104=9.64:1 cr
I'm assuming 120cc heads and some -deck height.
your exhaust valves should be 1.9's not 1.8's (I think, as 1.72 or 1.9 are the standard issues exhaust valves for bbc's)
Yes, not enough gear for 44's. You are running "an effective" 2.90 gear due the the extra tall tires. Like a 2.90 gear with 28 inch tire.