soundproofing a Sprite, can it be done?

["Evangelos G. Makris" <emakris@hol.gr>]

Whenever I take my dad out for a ride in my Sprite
(1966 Mk3) he complains about the engine noise in 
this car.

Besides the obvious under bonnet foam installation
(which I haven't done) is there anything else that I
can do to make the Sprite a tad quieter?

I don't have a plush carpet set. Just rubber mats
on the metal.

Evangelos