Well been waying up pros and cons for my d7 engine , looking at the d10 and d14 the only difference is porting, bigger carb 22mm to 26mm and big bore exhaust and higher compression head ratio , piston are all the same. so this is the route I'm going d7 bottom end 3 speed with high friction clutch plates and heavey duty springs, d14 head with rex's modified Suzuki 64mm piston and a centre plug head with the correct machining to get correct compression which has been supplied with the piston kit , and change the jets to suit .. should be good fo double figures 7.5hp to 14/15+ hp, for less than a couple hundred I think it's worth it .. baring in mind I'm doing most the labour myself ..