Are you referring to a rebuilt or what? What does decent mean?
I've seen 13B classified from $500 needing seals to $4K
Is it a 13BT? or N/A?
You can contact Atkins Rotary for their selection of stock engine...
www.atkinsrotary.com
And here's one mechanic near you. you might want to give them a call...
SRMotorsports
320 Fairview Ave.
Brentwood, CA 94513
(925) 516-7382
www.srmotorsports.com