ok you lost me you have a L88 427 parts and a built 390 hp ? or you want to buy a long block ? i would go the flat top or small dome lower CR hyd roller cam or soild if you want the sound and start at 489to 496 engine or use parts you have so you have ported heads intake and a bbc with a over bore of 100. over i hope its fresh bore there not much room left to rework bore if needed . heads could be over work and may not work very hot at low speed for the street use. i build mosty all bbc for street to strip 396to632 i have a engine machine shop. sell new and used parts . so i can help you on any level of this build or something that will work on pump fuel