To add to what everyone is posting, if you go with a front end from a 81-87 truck 81-91 Blazer/Suburban/Crew Cab, all you have to change is the core support, you can reuse the fenders and hood.
If you prefer the look of the 73-80 front ends, you will have to change the whole front clip ie, core support, fenders, hood, and bumper. Good luck, hope this helps!