Re: 406 top end combo thoughts...
Yeah I highly urge you NOT to go with a thumper.
That cam will outperform and out sound a thumper, especially on the 108 lsa.
I suggested a roller for longevity, efficiency, lower maintenance, less friction, lobe design, and if you compare a roller motor to a non roller in revving you will find the roller revs much quicker. I think my stock 97' truck will free rev faster than my hopped up camaro. I'm not a redneck that free revs all the time, I heard someone explain it to me and tried it.
Anyways, I'd suggest a roller with similar spec to what you have now though rollers are not very similar in grind compared to flat tappet cams.
I think Andy is onto something, if your piston to valve clearance allows you would benefit from more lift. .550-.580?
The only Mustang I'd ever own is a Fender.
'68 333" Camaro
'14 5.0 Mustang