When evacuating good used coolant, dont use the petcock. Coolant tends to splash chassis parts, possibly adding crud to the coolant, and can make a mess.
Find a clean 5 gallon bucket. Get about 6 or 7 feet of clear tube, 3/8" works fine. Put the bucket on the floor. Put the tube into the radiator at the cap and fish it down near the bottom. Stand back a couple feet and suck on the hose until its full, then drop that end into the bucket.
Come back in 10 minutes and all your coolant will be in the bucket, and you will not have one drop spilled or contaminated.
1988 F250 Supercab Longbed 7.3 IDI, C6, 1356, GEARVENDORS, 4.10 Sterling with autolocker
1986 F150 302, C6, 9" 2.75, Wood Flatbed