Transmission – Radiator – Pink Goo and my feeling of Dread

So I bought my 383 donor car that had been sitting for years. Checked the fluids and made sure it wasn't seized, all good. I hooked up a secondary gas tank and she fired up pretty quick. Well I noticed a trans leak but it wasn't red it was pink goo, it seems the radiator had an internal leak and let water into the transmission cooler. Anybody been through this? It seems like it's too thick to just flush out. Hoping to avoid a rebuild if possible.
Author: toomanycars