you need to have a donor car for the swap

first up remove the door lower plastics
then the kick panels
then the centre console as much as you can, the handbrake lever makes moving this a bit tricky
then the upper and lower steering column covers
then it's the lower drivers side
then the passenger lower side
then a pillers
then the dash surround for the instrument binicle
then the instrument cluster
then the top comes out

once it's all out you can then make sure you sort your wires out before commencing with the refit

the later dash had more screws and a different depth to the lower centre console mounting points so they may not go back in again but everything else lines up and plugs in

if you are doing the 92 spec swap though the outer cover is really tricky to get out as there are 7 screws and one clip and they are all hidden much better

once everytihng is out, you need to carefully unscrew all the brackets, remembering to keep the screws and fastening as the ecu panel is moved too as well as the auxillary fuse/relay panel

it's also a good time to swap the heater matrix and run any extra cables you may need for powering up an amp

you will also need to sort the stereo wiring out as the early models had different wiring for the speakers as well as 2 additional speakers in the lower dash you will need to remove

also, if you are doing the 92 spec swap the instrument cluster is a different size, not a huge difference, perhaps a few mm, but the hole in the 92 spec dash is much tighter to fit the early cluster into without removing the steering wheel first

and the most important thing to remember is that the 90 spec sierra's came with adjustable steering columns which the early ones didn't, and the surrounds don't fit pre and post so there may be a gap

you need to change the entire column from the intermidiate shaft upwards, so swap your steering column bulkhead bush at the same time

if you know what you are doing and have all the bits, you can do it in an afternoon, but if you don't, it's a mission that may take at least a weekend if not more should you find more problems as you go along

even with all this to consider, there are plenty of other things i have missed out before the read becomes way way too long, but having done this swap several times before, it's a peace of cake once you know what you are doing

and remember to label every since nut and bolt and wire as it's so easy to miss something