Lakland site FAQ:
NB: There's noticeable difference between "ash" (classic, think 70-ies Fender JB) and "swamp ash" (modern basses). Try to find out what year the bass was made and try luck in the Fender owners section to see what kind you're most likely to have got. Ash is much heavier, with a brighter responce and ringing clarity. Swamp ash is much lighter, bright but not SO bright, has this kind of expressive and stand-out sound that marks the sound of the bass in the mix. Alder is warmer and milder on the high end which, taken that this is a Precision bass, may be, and may be not complementing to the sound you wish to get.
Ash and swamp ash are essentially the same wood. The only difference is the weight. If you have a light ash bass (regardless of whether it came from the 50s, 60s, or 70s) it is essentially swamp ash.