One of the best items I have found so far for plastic repair. Available from ColorRite for about $35 plus shipping.
This kit is very easy to use and makes a permanent repair that can be sanded and painted.
Pictures below show repair on a broken tab on a 69 CT90 air cleaner housing. Unfortunately, you must have an undamaged part available to make the mold with the material that is included in the plastic repair kit. If you don't have a part available, you can still use the repair kit, but the repaired part may not look exactly the same as original.
Take some hot water and immerse the blue silicone form in the water. After the silicone is soft, make the form around the new part you need to duplicate. In this case it is the tab on the air cleaner. Let the form firm up and then take it off the the original. If you don't have a new part available to duplicate, you can use plastic, wood or anything else to shape the blue silicone.
Clean the edges of the broken part for better bonding.
Attach the formed silicone to the damaged part to be repaired.
Use the plastic powder to fill all the gaps.
Use the activator liquid with the dropper supplied in the kit. Make sure to completely saturate the powder.
Let the repair dry completely, then remove the mold. Inspect the repair carefully and add plastic powder in any voids on the underside of the repair.
Use a Dremel tool or similar to finish and sand the repair.
Sandblasted primed and painted part is shown on the top right.
Plastic Parts Restoration