All 427's have crossbolts mains be it top or sideoiler. A few exceptions are some industrial blocks that have been found used in irrigation and such. Other than that all production and service 427 blocks are crossbolted. As far as crossbolting goes you can crossbolt any FE block. You can use original or aftermarket caps. Both are selling in the $300 range today. For that money the billet steel caps are the better bet. To machine and install the caps figure $300-400 plus the price of the caps themselves. Some 64 and some later FE/FT blocks have the crossbolt bosses making it pretty easy to do. Blocks without the bosses just use a longer spacer with OEM caps. The billet aftermarket caps use no spacers and require a little more work from the shop to install because of the exact tolorance fitting needed.

G.