The only things I would change on that gun are the recoil spring and, if needed, the mainspring. It is possible the gun is setup for soft target loads. I would start with a standard 16# recoil spring and compare it to the spring installed. If the recoil spring in the pistol has a much lower rate, checking the mainspring is then needed. Or you can shoot powder puff loads in it. Say 230-grain at 650 fps or so or the Federal 185-grain Gold Medal wadcutter load (185-grain at 770 fps). Change the recoil spring and mainspring to 1911-standard to shoot hardball.
As far as value, that one is hard. While Jim Clark is a name smith and the pistol has historic value being built on a Colt commercial 1911A1, Bullseye is not the sport it once was. The modifications lock the pistol into target shooting. The number of shooters is down and the rules have been changed to open up the sport to more pistols and to optics. A new RRA Bullseye Wadcutter pistol with modern cosmetics/features (checkering, beavertail, sight rib) and fit is about $2500. I would guess that pistol would sell for about $1000 locally IF one could find a Bullseye shooter or a Clark collector.