I have built at least three mild street 4.25" stroke 383 engines. They work just fine. The most recent was with 452 iron heads with stock valves, homeported, 750 vacuum Holley, 1 3/4" headers, 0.5" hydraulic flat tappet and an Edelbrock CH4B ancient intake. It was actually pretty strong making over 490 hp and 600 ft-lb. The others have had aluminum heads, source and E-street which are pretty much the same. All with flat tappet hydraulics and stock rockers etc. They have all been pretty close, between 490 and 530 hp. And a tremendous low end with over 500 ft-lb at 2200. One was later converted to Victor style heads and a solid roller. I think it made a little over 600 hp naturally aspirated, still with the same relatively low CR short block. Basically you can do pretty much anything with a 383 that you can do with a 400 or 440.