Measure the spring width and the diameter of the bolts on the stock shackles and compare. If they match or close enough then they'll work.
Edit: assuming you have the toy's to measure I guess. Didn't think that one through before I started an answer.
If you are looking online at some part call or email them and ask for some dimensions or give them yours and what you want.
http://www.independent4x.com would be a good place to look for more Isuzu specific parts. Email them and I bet the owner can find something that he carries that will work.