Your goals are achievable with the correct good parts, a good sonic tested 400 block, 4.250 stroke crankshaft kit with the longest forged H beam steel rods you can use, 10.0 to 10.7 to 1 compression with a set of the new Trick Flow 270 CC heads and a matching intake manifold with a 1000 + CFM carb and a good high lift medium duration (245 to 265 @.050 with a LCA from 105 to 110)camshaft and rocker arm kit
My first 400 stroker (511 C.I. 4.375 bore with 4.25 stroke))had 9.25 to 1 compression with a set of mildy ported 906 heads with bigger valves and a low deck six pack set up. That combination made 612 HP at 5500 RPM and 644 Ft. Lbs. torque at 4500 RPM, I put that motor in a 3450+ Lbs. 1971 Duster that ran 10.69 at 124.+ MPH through the complete to the rear bumper 3.0 inch exhaust system on with the air cleaner on
A later change to a set CNC ported Eddy RPM heads picked it up 10.49 at 127+ MPH on Oregon 91 octane pump swill
That was back in the early to mid 2000 so don't ask me about the prices now
I beat the snout out of that motor, I did make a lot of changes to it in the ten years I owned and raced it but it was the same cam and lifters and bore size with the original pistons when I traded it off for my current race car
The cheapest way to make your HP goals may be a used lat emodel Hemi and a lot of NOS, no way to tell how long a stock motor will take 200 to 400 HP of NOS
A decent built pump gas BB stroker motor will make that amount of power for a long time, trust me on that