"You might search other makes to find an engine that is close to yours in displacement, rev range, HP, torque, etc and find i out which model and needles that engine uses."
While that method may bring results if you get lucky - the needles specified for various engines also depend greatly on cam profile and timing curves, etc. Years ago at an independent foreign auto parts store where I had a very good relationship the owner handed me a big bin filled with new loose needles and no clue what they belonged to. I had (still have somewhere) a little book with listings (all 60's and earlier). I sifted through the collection and cataloged those I could match. My reward was being able to set aside as many as I liked. An SU needle is measured every 1/8 inch--there are literally thousands of combinations. While there may be needles that will work better -- for the most part I think DX, KD and I think possibly KN needles were the ones that would work well in B18/20 motors. -- Dave