Guage cluster swap for tach

[TwoFiftyShifter]

My '87 K20 has non-tach dash with a gas guage that doesnt work well, and the amp and temp guages dont work. Just oil pressure and speedo. I have a '79 K10 parts truck that is a factory tach truck. How hard would it be to swap these out? Can I test the gauges out of the '79 to make sure I won't be wasting my time? The '79 tach dash is really cool looking, I'd much rather be able to hook that up then put an aftermarket tach on. Thanks for the help.