It sounds fine as it is a street car....you might be leaving a few hp on the table with the smaller exaust....but not enuff to worry about on a street rod.

You could always come off those headers with a 3 inch pipe to help some...not sure if they make 1 3/4 inch or 1 7/8 inch shorties or not....if it runs fine and you do not run at the track I would not worry about it.

If anything that tunnel ram is leaving more low rpm torque and hp on the table than those headers...unless you are running a huge stall converter or run it up to 7 or 8 thousand rpm all the time.

If you have a 4500 rpm stall and spend alot of time in the higher revs ,then yes the exaust is holding you back some.