Cosworth YB install query

[Brick]

Have a mk 2 Escort and had a Cosworth YB built for it. Used the "How to Power Tune Ford SOHC" by Des Hammill for guidance on the various bits and pieces required (has a YB conversion chapter). Have just finished adding on the necessary accessories, eg sender units, dizzy, manifolds, flywheel, clutch, etc.

Went to bolt the Rocket gearbox on and noticed the ring gear runs extremely close to the bellhouse (within 1mm). Is this normal? Everything I have read indicates the flywheel and clutch are larger between the Pinto and the YB, but nothing suggested regarding changing the flywheel. Likewise, have not read anything anywhere that indicates the bellhouse should not fit. Am I missing something somewhere?

Cheers