John is right,as usual. The later sixes boosted compresion for propane. I don't recall hearing this about the 270s. I'm not sure if Fenton made exhaust headers for GMCs or not,but Patrick's has the Chevy ones machined so they fit. I have a set on my 270. I'd stick to one carb,maybe a 302 two bbl set up. Why mess with multiple carbs in a quest for MPGs? Anyway,as John said,in fewer words, headers won't help at lower RPMs. Do your homework, and keep us informed of how it works out! There are folks here who Know.
