I got this email reply from from MSD tech support, thought it might be handy for the forum...
<blockquote><font size=1>In reply to:</font><hr>
The amount of compression the engine has, will determine the amount of spark plug gap you should use. Whether you step up in coils will not change the gap setting. For a good starting point, check out the chart below;
Up to 10.5:1 - 0.050" - 0.060"
10.5:1 - 13.0:1 - 0.040" - 0.050"
Above 13.0:1 - 0.035" - 0.045"
By the way I use .045" gap on my 351C with quench heads (~10.75:1), I have an MSD billet distributor, a Crane Hi-6 ignition box, and a Pertronix Flamethrower coil. To be able to boost the gap I believe the minimum you need will be to go from points to some form of electronic ignition, Pertronix on up.
What kind of gap do you guys run on your set-ups??
69 Sportsroof, 351C, 4spd toploader, Restomod BOSS 429 clone - the one and only (?) 1969 BOSS 351