the trailblazer/envoy fuel tank has several high spots in it and comes with a vent at each of those spots. you coild repurpose the stock canister those connect to or you could simply tie them all together into a single,larger, vent tube with some sort of filter on the end to stop dirt/debris from getting in. pretty easy to hook up the stock system if you want to re-use it so the system vents like it was designed. easy to do it the other way as well just keep the end of the vent tube higher than the tank so it doesn't purge raw fuel out after a fill on a hot day and then start to siphon fuel once the purge has started the siphon process. take the vent line up high then turn it down to keep moisture out and place a vent cap on the end, like found on a large truck differential or the like. some come with a short u shaped hose which could work on the end of the line to keep moisture out.
https://www.raneystruckparts.com/fre...r-kit-kit2902/