I would estimate almost 5" from the base to the prong, and around 10" over with all that hook so close to 15" long. MT bucks don't usually have real big heads or ears, but I'd say his ears are 6-6.5" long for reference, and also imagine the 6" length of a dollar bill and how that would fit across the prong or arc of his horn, or from the base to the prong. Just things I think about when guessing things like length and prong. His prongs are huge. I can't think of a buck that I've seen with prongs that great. They look especially big because he doesn't have a ton of mass. His right prong looks longer but they are likely both over 6.5" and the right maybe 7".
I'd guess his mass to be slightly under 6.5" on the base, but maybe a touch more on the first quarter. First quarter falls on the prong, so it will move down not up. How far down off the prong varies by measurer I've found. His mass above is what hurts his overall score as the half way point is well above the prong and unlikely over 4". 3rd quarter is spindly 2.5".
I'd guess him at 82 gross.