South Bend clutches are top notch. I have a Con FE in my 2000. It's a little on the grabby side compared to the Con OFE, but will hold more power. I opted for it in case I decide to go for bigger injectors in the future. Even with the slight grabbiness, I have no problems towing my brother's 24' Hewes aluminum boat loaded down with extra fuel and gear (close to 10k lbs. )
As far as power goes, you can get by without EGT and boost gauges as long as you limit yourself to something like the Smarty which doesn't tap the injection pump wire. Once you upgrade the injectors, or go with a box that taps the pump wire, like the Edge Comp, then you definitely need gauges.
I'm not up on the newest boxes, but I believe some of them have the on the fly adjustability combined with gauges that you mention. My Edge Comp has some on the fly adjustability without tapping the pump wire, but I'm not sure how it would compare to the newer boxes. It's just a fuel/timing box though--no gauges or display.
If you really want to do it right you should consider upgrading injectors in addition to the box. Your HO engine will respond to bigger injectors more than anything else, and mild injectors like the Mach 1 or Mach 1. 6 will also increase your fuel mileage a bit at cruise. With the addition of gauges, and free flowing exhaust and air filters, my Mach 1 injectors would barely peg 1250 deg. EGT with a fairly lightweight camper in the bed (1969 8' non-cabover Alaskan--about 1100 lbs). When I tapped the pump wire with the Comp, then my EGTs could climb into the danger zone fairly easily in 4th gear on my NV4500--and note that I have an aftermarket turbo to help cool EGT.
For you, (funds permitting, because this combo could easily hit $5,000) I'd recommend a South Bend Con OFE, Mach 1. 6 injectors, an appropriate EGT, boost and fuel pressure gauge package, Smarty, and your choice of aftermarket intake. Your stacks should make a very nice free-flowing exhaust system, as long as you've ditched the stock muffler--it's garbage and extremely restrictive.
In addition to performance stuff, you really should consider replacing the crap lift pump with something reliable. Avoid the dealer-recommended in-tank replacement pump like the plague. I went with one of the earlier FASS units and love it. Others are happy with their Air Dog pumps. Either one will be a huge improvement for reliability.
Mike