[Shotimes] Battery light and 10V at engine start

[van Oss]

When started, my 92 MTX consistently turns on the red battery light and the
voltmeter reads 10V.  One blip of the throttle and the light goes out,
voltage comes up to 13-14V, and it's good thereafter.  Started doing this
about 10 days ago.  Car has 83K and battery in trunk.

Sears just checked the battery and charging system and proclaimed both
healthy.  I trust the tech, he's got a blown Cougar.  He said there's some
loss with the battery in the trunk, and recommended a higher-amp alternator.

Do you concur about a higher-amp alternator?  If so, what are my options?
Thanks.

VO