Here is another vendor for you. I have only got about 1/2 the horses you do but the trans can take it.
I have had a LenTech in my cobra for over 10 years. the thing has never given me a problem. Like Fred, I have a switch to lock out OD if I want. A nice feature is that you can down shift from 3rd (or OD) to 2nd and it grabs right away. It won't grab 1st until you are going about 10mph but you have plenty of ponies to take care of that.
http://www.lentechautomatics.com/aodproducts.html
Harvey R