J. R. I had the most difficulty fabbing the cold side to clear the alternator at first, should have fabbed it in the truck instead of on the bench. I have been looking into using an HX55 or HT3b for my secondary on a new set-up I’ve been wanting to do. I have also been thinking of using an HX40 with machined exhaust housing for faster spool up as a primary. I’ve just finished with my 3500 a few weeks back, the usual mods, and now have the urge to begin fabbing twins again. The urge is getting stronger with all the talk of twins lately. Once again congrats on your set-up! I hope to see more folks take the plunge into fabbing their own set of twins.