I dont think you are WAY off at all.
I have a 69 Dart. 3300 with me in it( i am 320)
Bone stock 360 shortblock with replacement pistons 30 in the hole
Mildly worked eddie heads( my guy just looked at them and suspect they go 255-260)
Airgap
950
260/264 flat tappet, 565/565 lift
Dougs Headers 1 5/8 into bullet type muffs
5100 flash 8 inch. 4.10 gear
Car has run 11.26@ 118.40 with a 727
Has been 11.33 at 117.70 with 904( i know the 904 vert is not right)
Flat hood, no hood-scoop. Shift at 6100 usually.
Think it ran good for what it was. Just sold the shortblock.
Heads are getting some work, and they and the heads, headers, carb, etc are going on a 12.5 comp 418
