The answer is No..The Head bolts on the 4.3 Diesel are two sizes..The Larger Head Bolts which are 14mm - 2.0 are far too Big and Odd..therefore there arent any Superior Aftermaeket head bolts OR studs available..I have checked with the leading names of Fastener distributers and there are none available..Maybe some day when I become rich, I can have some sets made..the cost was around $1200 for a set of custom bolts for one engine only..however, it would be cheaper in bulk. There are studs that would work for the smaller 10MM - 1.5 bolts though..
So, are there any aftermarket bolt kits available that will at least work on the 4.3 Diesel?.. The answer here is also, No.
My advise would be..stick with GM Bolts here, and dont over heat the engine (especially with Aluminum heads), and dont advance the timing so much. If a head gasket does go, pull the heads and examine the gasket to find where it failed..then, get a strait edge and a feeler guage and check for warp in that area on the block and heads..then also, check the lengths of each bolt..dont be suprised to see a stretched one..Replace the all! Dont forget to check the small ones.
The M12 Torx head bolts have an update..The washer face (not the actual washer) should be no less then .112" thick..If they are less, GM reccomends not to reuse them.