I was thinking most smaller mounts will fit a larger slot if you cut or file them open. Odd dl chains doesn't matter if you make your own loops or have them made. A diamond cutter makes holes in anything. The bar rail disc is $20 if you have a router like bench setup. I don't myself. 063 ground rails from old 058 bars. Works out nicely for me. Keeping the really good ones for myself. The 18 and 16" 058s are good sometimes in D009 mounts. 375 chain was rather easy to find old partial reels from the 1990's listed for sale. Most people avoid it without pre-sets included, not me. Preset can be found and were. The bars were also older like the ones Mark is selling in small odd mounts mostly. Got two of those in laminated lp 14" NOS pro bars.
The steel on solid bars makes nice tools or blades.