On the dragstrip (not so much on the street) I started having issues at 400 hp with the stock lines and carter mechanical. Went to 1/2 pickup and lines. Didnt fix problem... sumped tank and electric pusher fixed it. So you are already doing better than i did with stock lines and mechanical pump. Fwiw
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'78 Macho T/A DKM#95, 460cid, SRP pistons, KRE 310 D ports,
3" pypes, Hooker 1 3/4" headers, hydraulic roller,
10" Continental, 3.42 gears
11.5 @117.5mph 3900lbs 
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