the options I know of are:
1) Bilstein matching OEM's part#.
2) Bilstein insisted the valving in that shock was not right for the application. You can send in your old shocks to be rebuilt w/the valving Bilstein recommended or order new ones w/the custom valving, Bilstein knows coach weight, shock length, etc and can provide the shock. WRV wouldn't spring for the custom valving cost so they ordered an off the shelf unit that met the length req'mt.
3) Koni shocks
4) Road King shocks
More discussion here
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