Let see if I can help you on this descesion, I have several motors that have been ran in my 3400 lb street, pump gas Duster. The first motor was a 512 low deck with 906 heads like yours, 9.25 to 1 comp ratio, with a six pak intake set up,Comp Cams solid roller cam, it ran 10:69 at 123 MPH with the iron heads. I switch heads (same compression ratio, 84 CC heads on both)to a set of Eddy RPM CNC ported by MCH, the car ran 10:49 at 128.5 MPH. The second motor is 446 C.I. 440 block with the same 906 heads off of the stroker, 9.46 to compression, Eddy RPM Performer intake,Holley 950 HP carb. Comp Cams XE284HL cam. This motor ran 11:30 at 119 MPH. Either way will pick the car up, I would do the stroker kit, 4.25 stroke or larger Make it pump gas freindly, unless you have unlimited access to E85