... any of you ever do a swap like this? Namely, I am wanting to install a SR5 dash into the ol' 89. Worthwhile or not, if so, what's involved?

What, no one has done this ??? Find that hard to believe!!!

i've never done this myself but tooling costs for things like wiring harneses are extremely high so chances are toyota used the same harness on the dlx and the sr5. i would just go ahead and swap the guages and see if it works. just try to get the guages from a 22r, 5spd, 4wd. if it does'nt work just resell the new guages.