If this were my radiator, I would call around and find a shop that can refurb the thing. Pull it, and let them clean, flush, and repair as necessary. Then just reinstall your brand new (rebuilt) radiator.
Most of that "gunk" is what happens when tap water is run with the coolant over the years. I don't put anything into the cooling system that is not anti-freeze or distilled water.
Stick with [green] anti-freeze.
I would cap the currently unused transmission lines.
I am not a huge fan of aftermarket radiators and also not a fan of installing aluminum radiators on otherwise OEM engine combos. Some of these other guys, however, will be better at pointing you in the right direction for a replacement if that's what you decide to do.
Give this a look when you have the chance: https://sterling-radiator.business.site/
Most of that "gunk" is what happens when tap water is run with the coolant over the years. I don't put anything into the cooling system that is not anti-freeze or distilled water.
Stick with [green] anti-freeze.
I would cap the currently unused transmission lines.
I am not a huge fan of aftermarket radiators and also not a fan of installing aluminum radiators on otherwise OEM engine combos. Some of these other guys, however, will be better at pointing you in the right direction for a replacement if that's what you decide to do.
Give this a look when you have the chance: https://sterling-radiator.business.site/
This thread may interest you....
Upgrades radiator that’s not a 3 core??
My stock radiator has a crack and needs replaced. This is a mostly stock cruiser so I don’t really care to do electric fans or a huge radiator. Is there a decent middle ground? Something better than stock but not a 3 core? Car is a 91 5.0 manual with stock fan and working ac.
I second getting the original one repaired as the new "stock" replacements are terrible quality wise. If you have any inclination to increase the performance of the car just bite the bullet and put an aluminum unit in it and move on. I use and can recommend a Fluidyne however they are pricey but you get what you pay for. You can find them cheaper than on Fluidyne's site but it has the best info:
SVE will be one of the cheapest but do some research before you go down the aluminum radiator route. Cheap usually means overseas and the quality tends to not be as good as Americal units made like BeCool, Champion, Cold Case, Fluidyne, Griffin, etc. (pretty sure all of them are still American made). The only other one out of that list I can speak for is Griffin as I run one in my T-Bird.
FHP30A-93MU 79-93 MUSTANG AUTO RADIATOR - Fluidyne
Upgrade your 79-93 Mustang's cooling system with Fluidyne's FHP30A-93MU Auto Radiator. Enjoy enhanced heat dissipation for optimal engine performance.
SVE will be one of the cheapest but do some research before you go down the aluminum radiator route. Cheap usually means overseas and the quality tends to not be as good as Americal units made like BeCool, Champion, Cold Case, Fluidyne, Griffin, etc. (pretty sure all of them are still American made). The only other one out of that list I can speak for is Griffin as I run one in my T-Bird.
Mishimoto is another brand of aluminum radiators, and they are made exclusively in the good ole USA.
If the shop does it, you shouldn't have to do anything. It should come back looking like brand new.