I would have to see the other drums to put a price on the kit. The person that would choose to "retrofit" a vintage early 50's round badge Gretsch bass drum may not be working with a full set of tools....literally and figuratively! The retrofit is probably not a clean job and may not easily be reversed. IMHO, the kit is not complete without the 9X13 and the original rail mount system anyway. More pics would be helpful but generally, the Round Badge Broadkasters (22x14, 16x16, 9x13, 5.5x14) don't hold their value like the smaller jazz and bebop sizes.