Magnum 300 crate engine - how should it go when tuned up right?

I'm a novice when it comes to tuning so I could use some perspective and advice here.

So far, I have ~750 miles on the Magnum 300 that I bought used from a good guy here on the forums. The motor is tight, doesn't burn oil, good oil pressure, no leaks...idles great too.

Performance isn't impressive at all.

So far, I haven't messed with it too much but subjectively, it doesn't feel that much better than the stock 318 2bbl when it was running at its best, especially in the low rev range. The Demon 650 carb is probably due for a rebuild (this winter), there's probably some timing advance left on the table, carb could probably be leaned out a bit...so I know it's not optimized. Yes, I realize that this is a mild motor with relatively low compression and a very tame cam but on paper, I thought my setup would be a bit more lively.

Stock cam/heads
Demon 650cfm
Mopar Performance M2/dual plane
Doug's long tube headers through 2.5" (no crossover)
4.10 axle ratio/27" tall tires
2600 rpm stall
Mildly built A904
5900 RPM governor weight, TF2 shift kit

What would you change first?

I'm still running a steel fan (electrics are sitting in a box), mufflers are probably restrictive (cheap-o Summit type)...could those be pulling off that much power?

In CT, we have access to 93 octane...how much timing can folks get away with? ?

Any thoughts are welcome.