A stock 307 with 60# injectors at 100% DC (this is worst case) and 20 psi boost will have enough volume for a max of around 64 psi total rail pressure (fuel flow will be around 60 gph). If you need a duty cycle of 90% or less, it will support a max of 68 psi - and obviously with even less DC you will have more rail psi; 80% will put you over 72 psi.
If you were to remove the pump and shim the relief (and I used to get flamed for this all the time but I did it and it worked fine - they say the 307 doesn't have as beefy an armature as the 340, but whatever), you can get about 4-5 more psi under the same conditions above. I.E. at 100% DC, you will end up at 68 psi or less, which is 45 base plus 23 boost. I doubt you will want/need to run 100% DC so that will be plenty.