Many different ways to skin a cat
On my 350 motors, I made a custom pilot that takes place of the ball bearing and used a shell reamer to ream the crank bush
I also mounted my TS crankcase on my milling table and bored the crank bush inline with the opposite side
Keep your options open
I must admit that with a properly supported SHELL reamer you would be in with a chance on a soft material like bronze . I maintain however that with one of those adjustable ones with the long blades or a standard length machine reamer no way .
here's the thing , you have to have some clearance between the pilot end and the bush , Even at at absolute minimum sliding fit clearance on something only maybe 3/4 long you will still get lateral movement over the length of the crank . Unless you make your custom support collar dam near as long as the crank in which case it will likley tip in the bearing housing when it is force to cut unevenly
Buy the time you have done all that it would have been quicker to do it on a mill , i maintain that the only way to cut off center on an existing hole is with a single point cutter
IF you are doing many cases probably making some custom fixture is an ok compromise using a shell reamer OR an adapted "David Brown" style adjustable reamer (not the floating blade type those will DEFINITATLEY just follow the hole no question at all ) the ones where you adjust them with a grub screw in the point with split blades that can move a few thou ,,, i used those extensively and man you sure can get accuracy with them and they repeat! but how many machine shops will have or make the required special support fixture without charging 1000s ? Most machine shops dont even know what a "David Brown" reamer is !
Just out of interest , shell reamers arnt adjustable ( unless its a terminology thing and what you mean by shell reamer isnt what i understand them to be ) so how do you use them for more that one size ? unless you have like 400 of them all made to specific sizes?
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