222rwhp! boy is my face red.

Hi fellas, I feel I need some advise on this one.
I had my Valiant on the rollers a few weeks ago and Im very embarrassed to say it only made 222hp at the tyres.
Its got a 440 in it!!! I thought at least 250, I was praying for 280.
Anyway, my thoughts are that the exhaust is restricting it the most,
its only got early70's centre drop manifolds and 2 1/4" pipe into a single 3" with a hooker muff.

initially I bought a 1 7/8" weld up kit, but abandoned the idea when I found
id be killing ground clearance by about 4" :angry7: and any uni-body modification (eg: fenderwells)
will mean I have to run a cage to go faster than 12.50 :angry7:

the motor is a 10.5comp 440, unported 906's, factory iron 4bbl intake, 800 holley, 1" tapered spacer,
crappy exhaust manifolds and the cam is 235@50 .507" lunati, with 1.6 rockers so about .540" lift,
lunati recommend it put in at 104deg but I put it in at 102deg to try and stop reversion :oops:

At this point I think Ill put the cam back to 104, build some headers for it and get myself a holley street dom intake for it.
what do you think? any feadback would be great, thanks Tim.