Re. carb boots for BS34: ARS manufactured the original items, which have held up to 10% ethanol fuel for decades. ARS boots are still sold under the Tour Max label, available from 650 Central or any shop with a K&L Supply catalogue. ARS boots have vacuum barbs which are useful for connecting a manometer, but you'd need matching metal shrouds for support, and those are hard to come by. JBM boots are made for use without shrouds but have no vacuum barbs. 1977 was a good year for BS38 carbies and if yours are anywhere near saving you might consider rebuilding them or sending them to Oldskool Carbs for a rebuild: search the Shops forum for contact information. Read the Carb Guide (linked in the Tech section) and kopcicle's thread, "carburettors from the grave...." And if you have the OE airbox, I'd strongly recommend that you use it.