to run a yb motor n/a requires a very heavily ported and polished head which is very expensive
my pal has a n/a cossy mk2 escorton twin 48,s and it makes 205bhp and revs to 10000rpm
but has nice fat torque curve so pulls very well

you would be better transforming your std pinto engine to run the cosworth yb crank and rods ,thus increasing your rev limit and also being steel can handle more abuse .
this and some headwork on your pinto head along with a set of twin 45,s should see a strong 185 + bhp