KGB,
I have gone to Purina feed site and, after doing a retailer search, can't find anyone in Southwest Oklahoma or North Texas that has High Octane Fitter 35 in stock.
I have 2 barrows at around 260 lbs. and need to hit the brakes on weight gain ASAP.
Any help you could provide would be great.

Powerfill is the original product for managing weight gain.
3 lb/day = 1.0 lb/day gain

If you need less:
(Total daily feed; divide into 2 equal meals):
Powerfill. 2 lb
Champion Drive. 1 lb
Depth Charge. 1/2 lb (8 oz)
The pig should gain about 0.75 lb per day.