i have considered doing this with my ke15, but thought it isn't really worth the effort. there is no simple bolt in option. i have retained the standard stud pattern, and simply gone to mazda 13x5.5" steel rims, as they fit the car perfectly and allow me to run decent performance tyres in 185/60r13.
yea, the front is easy. just bolt on later hubs.
the back is a different story. you could adapt a ke20 diff housing as it is the next narrowest housing, and do a ke30 axle swap (need to trim each axle splined end about 3mm) to that to get your 4x114.3. the only problem is that it will be about 50mm wider which will limit wheel selection, unless you want to start flaring guards. doing the above swap won't make any difference strengthwise, you just end up with bigger self adusting drums and your 4x114.3. also you will need to fiddle around with handbrake cables and moving diff mounts.
maybe look into getting your existing axles and drums redrilled?
maybe you could investigate a rear axle from a datsun 1200, or 120y or something, to get the right width?
other than that you could look at something stronger and get it narrowed. but that is a bit overkill for a 3k.