hey i have a 440 rotary valve eng type 454, it has a head with inserts and nickisil cyls. i took it appart the other day and found cracks between the big and small exh ports.looked up this eng at the dealer (98 440 x) and it shows steel sleved cyls and a 1 piece head. any ideas ,i bought the eng used so i dont know whats up. only nickisil cyl 440s i found were non x models,what gives. any ideas guys. anyone in canada with a cyl 4 sale.