I hesitate to tell you because you would be much better off not going draw thru, but turbonetics still does ceramic/carbon seals for draw thru. The boat guys still do this for some reason, and turbonetics still caters to them. I dont think you will get any GT series turbos with these seals, but efficientcy doesn't seem to be high on the priorities of this build anyway. There are still alot of good turbos out there in non-GT variety, and they are much cheaper.