I haven't done the big bore yet but here is the thread with my current build info (Carbs, cams, head work, high compression 865 pistons and TTP igniter)
Zmilins build If given the option to do it all again I would. If not for my mistake and bending my valves the install was, to me, easy.
A 904 BB will gain you more torque over the 865 even with the minimal cc increase. Still worth it and its really the only bolt on big bore you can do without machining the cases.
You want a bit more, you wanna feel like your getting some ccs for your money... go with the 994 big bore. The only dyno Ive seen for that is on an EFI bike but it got him up to 80hp/63tq.
994 EFI BB Whatever you do my recommendation is
TPUSA for your performance needs.
