Zack Before you go crazy on this problem, have a couple of ideas to try that will not break the bank or wallet. Hold off on the pump first off. From the old days, not to laugh
I worked on a SCJ Torino with a 429 topend and 460 block. This thing always ran hot until we did some things to it.
We ran a water pump for AC system whick had more impellors than the car without AC. Like you said the car needed more coolant flow. We also found that the impellor was solid plate that was riveted to the impellor. This is an easy thing for you to do,
Get a pair of water pump gaskets for the block first. There where kits in Summit and Jegs for these kits. All it was was a thin steel disc and 3 or 6 rivets depending on how many fins are on the impellor of the water pump. The rivets where short 1/8" or 3/16" Enough to hold the 2 parts togeather. If you don't have a thin piece of steel or aluminum go to Lowe's and get a piece of 12"/12". You are going to make a circle to rivet to the impellor. The easy way is to find a can, cup, or compus to make the circle. You want to make it just small enough to spin inside the waterpump housing and not hit anything with about 1/4" clearance. Drill holes in the widest part of the impellor in the middle and rivet it a minimum of 3 times. I do mine on every impellor fin. Reseal the back of the waterpump. If you are careful you can reuse the gasket or go with a thn coating of RTV and let the sealer setup for 24 hours, this is a must. If you have the gasket in good shape, I spray them with hi-tack and let them sit for an hour. Reassembly pump on motor.
Next, what temp is the thermostat? Is it a 180F or 195F? Here is another problem, I am hoping you have all the air out of the system, we had a real problem with the SCJ and air pockets. We had to burp the system about 4-6 times to get all the air out. Lets get back to thermostats. Pull the stat and check the temp on it. If you get alot of heat out there, 180F is fine. Make sure there is 1 or 2, 1/8" holes in the solid piece of the therostat. This is to help remove air from the system when or if it gets air bound. Next go to the local Autostore and find thermostats. We are looking for a stock one with the largest port in your temp reading of 180f. The housing may be a little bigger but we are going to trim it down to fit. The FE motor I have uses, a BB-RB motor from Dodge, 383/400. The port is 1/4" larger for more flow that the FE one. I race autocross and roadrace, Motor doesn't go over 200f even in 100degree temp. Get a water housing gasket and thermostat that looks like it will work. FORGET about those highflow $25.00, antistick ones. IMOP they are no better than a good Stants one. Go home trim themostat to fit in manifold flush or outlet housing. Drill 2 holes 1/8" at 180 degrees apart. If thermostat is vertical, you want a hole at the top of the housing, thermostat laying flat doesn,t matter. Install new gasket, install waterpump and fill with coolant, Burp the system a couple of times ad go for a road test. They sell a funnel kit for about $30.00 is clips onto the radiator filling spot and will let the motor run without having to keep opening and closing the cap.
These things will be more about your time and saving you a $100.00 or more for the price of a new pump that will not do anything to help your problem. When you get your water pump off the motor and the inspection plate off, if there is a disc already on the impellor, this means you already have a highflow waterpump and we need to look in a different direction, still checkout the thermostat port for size. We may need a different pulley for the water pump. Good luck Rick L.