So I'm looking at buying flowtech headers #31150FLT. I've heard only certain brands like hooker headers will fit the 71 cutlass without and modifications like the starter and fuel pump. Has anyone tried or heard of anyone bolting these on and running then with no issues?

 

I have never heard of any clearance issues with the fuel pump. The starter is another thing - many headers need a tube to be slightly flattened to give clearance. I had to do that on the Heddman Headers on both my 70 and the 71. It's not really a big deal and apparently hasn't hurt anything in the 20+ years they have been on the car.

I don't have any experience with the FlowTechs, though.

 

Don't get those headers, they are not straight. the collectors are terrible, as they point in different directions. usually any direction except straight.