I opened up the cracks with a v cut and used an epoxy from the hardware store. It had to be in the early 80's it was on my MGA and I finished it in 84. I have put about 6000 miles a year on it. I mixed it in a syringe without the needle and used it to force the epoxy into the crack. You could probably do as good with a toothpick. Sand and paint.
