Hi,
I'm a long time enthusiast & looking to make my first purchase ASAP.  I would love some advice.  
I'm looking at a 1998 Everett-Morrison Cobra.  It's listed as recently completed with less than 500 miles.  Paint & exterior recently finished & looks great.  Engine starts & runs great, sounds great, but haven't driven yet because of the weather.  
How can I tell if there has been more mileage put on the engine & if it is really a new engine, and if its been sitting mostly over the past 20 years, what are the risks with the engine & tranny?  It has a small 
oil leak which appear to be off the passenger side rear valve cover gasket & leaking down to the 
oil pan.  I can't quite see it, but I am concerned it could be somewhere else off the engine or rear main.  If that was the case, what would it cost to repair.
Any advice one E-M quality?
The engine is listed as a 383 stroker & claims 500 hp.  Without a dyno, can I even be sure what the hp is?
Their is a 6 speed trans, not sure of the gearing.  I haven't seen many Cobras with a 6 speed.  Why?  What would be my concerns with getting a 6 speed vs. the 5 speeds?
Would love to buy the car, but don't want to end up putting another $10k into to fix the motor or trans.  I'm not opposed to putting money in, just don't want to miss any major items.
Tires, rims, & outside looks new.  The seller has mentioned to check the alignment & comments I may need to get an alignment done.  Sounds like a red flag, but not sure if he knows it needs.  The seller is the second owner & said he picked it up unfinished & comepleted out tuning the engine & finished the paint.
Any other recommendations on what to look out for, frame looks pretty good.
Thank you for the feedback.