Hello Everyone.
I want to first thank you all for your information, help and kind words i really can not say thank you enough for your help. It is very much appreciated. If i wasnt so far away i would gladly buy everyone a beer and a pizza just to say thank you for your time and help.

I think the first thing that is best to do is to double check all my measurements and make sure i know all the exact numbers and where i currently stand before proceeding.
As i do not wish to waste anyones time with wrong numbers and wrong calculations before moving forward.
Again thank you Blair,Barry Falcon67,Captcobrajet and yellow truck plus anyone else i forgot.
I kind of wish now i had purchased the mahle dished pistons

theres me thinking the flat tops and 76cc 427 medium riser heads matching the factory c7zx dual carb medium riser intake manifold would net me near 10.8.1 just slighty higher than stock 10.5.1 and would be ok.However you live and learn.
I will get all my measurements confirmed and report back. I will double check the rear axle ratio as well. The reason being the axle ratio is tall(low) The roads over here in the uk are more twisty and smaller and its normally short lengths of road for example 1 mile long road then you reach a roundabout or a T junction or a set of traffic lights. So unless you go on motorways(highways) most of the time the power is from idle to 5500rpm if you have enough road to reach that in each gear before corners,lights roundabouts ect.
So most of the time the power is need from idle to 5000-5500rpm.
Again thank you for the help and advice. One more question as well if i was to go hydraulic roller camshaft would that then mean i need roller rockers on the valve train. As i have had the original 67 shelby gt500 le mans valve covers restored and would like to keep them and use them as i was not sure if roller rockers would fit under neath the stock valve covers.
Thats why i figured stock valve train just upgraded with heavy duty shafts, end stands and spacers would be best and what with the rpm goal 5500-5800 max i would of thought that would be ok?
Again thank you all for your time i will double check my measurements and get back to you all.
Thanks again everyone. Stay Safe
Best regards
Dave