I have a new XR upper and an extra B1 lower. Just running 600hp. Now I need to find a short lower case.

If it works out for you and you want to sell the empty spare std bravo lower down the road let me know, Smitty

Will do. Thanks

Yes they will, what you're looking to do is a Bravo I to Bravo IV conversion with cryogenic parts and replace the Mercury lower unit with an IMCO SC Extreme lower unit, this way if you have a ITS or XV box the Mercury Racing Helmet will still work with it, but the IMCO lower unit is more aerodynamic and causing less prop slipage. This conversion will hold 1000 HP without any problem, I have one, an XV Box with a Bravo IV-S4C Upper Unit and an IMCO SC Extreme 1.35 Lower Unit, with a 34" Maximus Prop. it runs perfect with a Blown 525 EFI turning about 950HP.