I have no comment on whether you re-test with the WISC-IV (or, preferably, WISC-V; now out a year, the -V is recommended over the -IV, because of norm obsolescence--and I like the index structure better), from the standpoint of providing access to programs; naturally, that would be a family decision.
On the KABC-II, it is a solid instrument, and entirely appropriate for assessing giftedness. The more significant factors in your DS's scores are likely to have been not the instrument administered, but his age and disabilities. Depending on the pattern of performance, it is also possible that you would have scores that align better with your experience with him if alternate composites had been computed. (Though I must say his index scores are not extremely diverse; 90th %ile is only one point off of the Superior range.)
