1998 Chevy Express valves

the block was changed because you have roller lifters. the earlier block did not have this. the only thing i can suggest other than changing the block itself is to see if someone like crane or one of hte aftermarket cam manufacturers have roller lifters that are hydraulic. Most of them are solid lifter. Also the push rods are shorter due to the roller lifters in the newere truck engine. You cannot use the hydraulic lifters from the 76 engine on the 98 cam as the it is steel and will eat the lifters/cam up in nothing flat, unless you have done that already. You can get an engine out of a 96 up i fyou like. that will be your best bet.