My advice would be to get an S14 elbow and S15 front pipe, otherwise you won't be able to fit the front pipe support bracket... I believe the S15 Blitz front pipe is a good price. :nod:
Alternatively you can machine/fabricate a 3 hole flange copied from the gasket. Bolt on the flange first then adjust the angle of the down pipe for welding to minimise angular stress on the elbow and down pipe.