there is a video on limewire/kazza/imesh etc of some jap guys building a very tough 4AGE, then tearing down a T-50 and putting a trd gear set in.. then LSD.. then clutch.. then the same for an AE101 levin... it's big.. but it shows exactly how to change the stem seals with a cross section 4age head they have sacrificed.. or just go to any engine reco place and say can yiou pretty pretty pweeese put these in... thats what i did i know i cheated..