It probably is possible to find a 6 tooth spur drum. And the oil pump drive worm gear. The small spline rim sprockets in the larger 3/8 chain are smaller in diameter. They will work but not ideally. Look up the bar for say the 540t or an Oregon mount 095 and 3/8 lp. The genuine picco bars that are a better match to the genuine picco chain in that the rails are a couple or so thousands thicker, at least with laminated bars I have encountered. A Stihl bar, 3005 mount, will need the slot lengthened, and most likely new oil and adjuster holes. Just do not locate the new hole close to a spot weld.