These 3.1 engines use a "zero lash" rocker assembly. Because of the design of the intake manifold, it is impoossible to access the rocker arm nuts after the engine is assembled, so the rocker arm nuts are torqued to a value instead of being lashed. As these engines get older, clearances increase and the lifters lose some of their spring tension causing the "normal" lifter tick associated with these engines. Since the motor sat for a while before you installed it, there is a good chance that you have sludge in the lifters increasing the likelihood of a tick. My suggestion would be to continue to try extra oil detergent additives for a while to see if the noise goes away on it's own. If it doesn't, I suggest taking the valve covers back off and manually working the pushrods in and out of the lifters to force the hydraulic portion of the lifter up and down in the bore. This may free any that are sticking and eliminate your tick. Also, 95 was the last year for a flat tappet cam, all 96-up had roller lifters. I believe the torque spec is different betweent the two, as is the intake gasket. IF you had the intake off the replacement engine, make sure you used the proper gasket for the year of the engine. Some 95's had the roller lifters also, so it's possible both motors are virtually identical, but there is a chance that you put a roller motor where a flat tappet used to be, so be aware of these differences when replacement parts are needed later on.