Mc ??

wel my MC went out on my dart, so i replaced it.. and the only one i could get was a 1-1/32 bore.. and well they suck. so i was wondering...

If I went from a 1-1/32(26mm) bore MC to a 13/16 K-car(21 mm)then I will have more PSI but less volume and more pedal travel correct?
if I bought a MC adaptor and used an alu MC from the K car which has a 21 mm bore which is close to 13/16 bore but smaler then the 15/16.. will that be to0 small of a bore? Reason i'm asking is I need a MC and so far havent found a 15/16 bore localy(carquest is looking).. But i have a good K car MC FREE other then the adaptor..also I am not sure of the ftting sizes either..
My GM caliper bore sizes are 2.5 in or 63.5 . The 75 dart Caliper bore size is 2 19/32 or 66 mm.

Basically which MC would be a better match for my disc.. the 15/16 or the smaller 13/16?
Thanks
Don