the talldeck 10.200 block is not a drop in .if you only staying at 500 hp and only 427 getting the enging to fit is not worth the work . there two ways to go with this build up take all parts less pistons use a 454 block and build a 427 out of it . or start build with a 9.800 deck block with Gm 454 block you can get to 512 cid with out much work built many of the 489 to510 . i have done many of the 10.200 tall decks but we start at 572to 632 cid then it,s worth the work for things to fit .