Should I add an EGR?

[83 Scottsdale]

I have a 1983 K10. The original engine was a 305 but it was swapped to a crate 350 before I bought it. I was diagnosing a problem my truck had, and I read somewhere that the EGR could be plugged which was causing the problem. So I looked at my engine and I found that I don't have an EGR. There is a plate bolted on where the EGR should be and the manifold vacuum line is plugged off. So I'm thinking that when they swapped engines, they didn't put the EGR on. I did more research on EGR's and apparently they add 1-2 mpg. My question is if I should buy and EGR and install it, or just leave it? I think they run about $50-70 so would it be worth it or not? Also, would it mess with my timing? Any help is appreciated!!!

Thanks.