Your almost never money ahead trying to retro fit existing shocks, they usally are not valved correctly sprung rite or the correct compressed and extended lengths, that said Banshee front shocks used to be the closest fit there 1/2 longer 14 3/4"
 If you could Find used ELKAs I can trim shock bodies or you can buy the correct lengths then you could order the proper shim stacks from ELKA and be very close.
as far as OEM shocks early YFZ 450 are 15 3/4 and have been used with Frame mods to be good with OEm a-arms. If you want to get new Arms Lance at Metaltech can configure something for you .