Pay special close attention to the cheapie 383 stroker kits. Make sure you're getting good parts, such as forged pistons with correct pin height, new correct-length rods, quality crank, bearings, rings, etc. Pay attention to what your resultant CR will be with the heads you want to use. Your swept volume will increase by 4.125 CID per cylinder which will up your compression ratio. The 400 SBC crank has a 1/4" longer stroke, 3.75" vs 3.48" so you will have to clearance the block for the rod throws. Have the block zero-decked to prevent the slugs from being way down in the holes. Most high HP 383s require custom rebalancing and 4 bolt main caps.
A well built 383 will outperform a 350. Careful parts selection for your application is important. Most machinist/speedshop guys may assume that the 383 is for racing, and pick parts accordingly. Make sure you don't build a race motor that has no place in a work truck.
