Can Mace advice on how to properly install the oe-r lifters and if they are worth too? As I would be running a XP hot cam and read that people having troubles with installing them and face noise issues too.

I believe the Comp Cams oe-r lifter are a performance anti pump up lifter. These type of lifters are set with very little pre-load or lifter crush, this can create extra noise in the valve train. Generally speaking if the standard lifters are ok then those will do the job fine, otherwise we supply the Crow Cams performance lifters which are a good upgrade from the standard lifters.