Why not consider a hydraulic roller cam. And on a 4" stroked 340 with a single plane, there won't be a lack of power below 4500 rpm. The M1 single plane is rated from 3000-6500 and with a 4" stroke it will be lower than that.
I'd go with more stall(like 3500+), scrap that vacuum secondary for a HP Holley DP, and maybe cosider some long tube headers. If thats not enough, some Edelbrock heads should wake it up! Just my 2cents.O:)