I will readily admit I'm not the brightest guy so here goes. I have a mildly built 350, small cam, headers, etc and a 700R4. MPG is horrible and I know for a fact the lockup solenoid is not wired. I found this write up 700r4 lock up confusion - Hot Rod Forum : Hotrodders Bulletin Board
However, I do not know if the power needs to be on a toggle or if it can be hot all the time while running. According to that write up it would only lock in 4th so my brain tells me it doesn't need to be on a toggle, just power while running. So, toggle or no toggle?

 

Locking up the t.c. isn't going to change your gas mileage from horrible to good, unless maybe 1 mpg better is how far away your mileage is from being considered good.
Not quite following your toggle or no toggle question. If you're hooking it up to lock the converter only with a toggle switch, what's the question? You only want to lock the converter once the trans is loafing in 4th. Lock it up in the lower gears, and you could break the lockup clutch inside the converter, it's not made to take the amount of torque you'd be giving it if locked in 2nd or 3rd gear.

 

My question is, since I only want it to lock in 4th gear (and that's what that write up suggests would be the case wired that way) would I need to have the power on a toggle switch to turn on and off manually or could I just have a "run" hot and give it power all the time the engine is running? I'm not expecting miracle MPG gains, but every little bit helps when you get 10-12 on the highway.

 

No, you can't run it hot all the time, for possible damage reasons I described above. Also, you have to start out with the t.c. unlocked or the engine will kill. Think of the lockup function as an engaged manual clutch. If you don't switch it off when you go to stop or start the car, the engine will kill. So that's another thing you need to be conscious about if hooking it up only with an on-off switch, you need to remember to switch it on when the trans is in 4th, and off when it's not. Another option is to still switch it on when in 4th, but also wire it through an auxiliary switch at the brake pedal to turn it off, much the same as how the disengage switch for cruise control works.