gear reduction starter

[Carole and Jonathan Quandt <fourqz@earthlink.net>]

My starter on the 100-4 has given up and it is hammered . the  
reduction starters being offered on ebay etc. seem to offer an  
economical alternative to the orig. plus no core charge ( as much as  
$300 ). This is not a concourse car so I do not care about all that .  
Is there one brand or other that might be best? Is it    necessary to  
reverse the ring gear on the flywheel ? Thanx for your input, Jonathan