62 Bellhousing Thread Repair - Insert?

[bhap]

I have a 60-62 hydraulic clutch bellhousing with the rear engine mounts I'm planning on using in my 62 C10 when I swap engines to an L31 crate. While cleaning it up, I noticed that the two rear mounting holes are "loose" when I thread a 1/2-13 bolt into the housing. I'm trying to decide if I should use a helicoil, EZ Lok or something else to repair the threads? My experience with helicoils has been hit and miss, and I have not used an EZ Lok. EZ Lok's have a pressure activated coating on the outside that is supposed to hold the insert from coming loose. They use standard taps on the outside so install will be a little cheaper. Any suggestions on which is going to be stronger? And "while I'm at it", has anyone threaded the two lower holes for the transmission to mount to? The two lower holes are not threaded so I'll have to use nuts inside the bellhousing. The bellhousing is cast iron.

Thanks for your help.