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If I am not mistaken, these should be a "firecrater" type piston, middle is for 706 top and bottom is for M: 
Notice the depression where the sparkplug locates. This is another style piston, I think these are from TISCO: 
I think that these pistons are the most common today, at least the majority of domed pistons in the boneyard are this type. Another type of piston I have found is a flat type dome. I dont really know who makes these, but im guessing A+I? 
M&W (now Pow'r seal made by herschel-adams) also has a different style of piston. Think of a flat top piston with a dished center and two half moon domes. I have a vintage M&W ad from around '69 that has pictures of the domes and lists all the available part numbers for about 100 tractors. This ad lists 5000' and 8000' pistons with the 8000' being used in the distillate head for use with gasoline, or used as an lp conversion for tractors with a gasoline head. I imagine those 8000' pistons have some pretty lumpy domes on them.
I think IH also had different dome sizes. I think they had a 5000' a 8000' and if im not mistaken a 12000' for really high altitude lp (someone please correct if wrong) Nowadays I think that only the 5000' is made. If you ask 100 different people what the best piston is, you will get 100 different answers. Or in some cases none, as nobody knows or those that do dont want to share info. Nowadays I think that only the 5000' is made. With the TISCO pistons and a 450 gas head should put you about 165 psi. With a 4.125 bore and a good tune should make 65 easy.
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