Mustangs Unlimited (800-243-7278) has owner manuals for '93 @ $24. each.
They also have the complete 1993 Mustang Service Manual for $120.
Heres a link to the website:
www.mustangsunlimited.com
Your stalling problem may the IAB and/or the TPS. Remove and clean the IAB and check the TPS for proper voltage and operation. A new TPS is about $35. from Ford. A new IAB is about $100. but they can often just be cleaned to get them functioning properly.
Converting to manual is a $2,000. + project.
The best way is to get a wrecked Mustang 5.0 with a manual and use all the parts from that, replacing the clutch and other parts that need replacing.
Nitrous Oxide (
NOS is a brand name) is easily available at many aftermarket suppliers.
Get a copy of any Mustang magazine and they will have tons of ads for various nitrous oxide systems. I suggest you not go for too big of a shot on a stock engine.