I looked at some info from jbl obsolete specs page and I think that with the right tweeter attenuation and a crossover above 5 khz, you would have a NICE speaker. That tweet doesn't handle as much juice as the 8", so you want to pad it down anyway. Attenuation about 12 dB would be a good starting point. That 8" has a rising response from 1.5 to 5 Khz and would be good with pseudo butterworth. I guess about .3 mH coil ought to do it.I am no expert, but I bet these would really cook!
Have fun and let us know what happens,
Thomas