Uh,,,, don't ask me, I'm pretty sure they go in the 50's, or 60's. Yeah, thats the ticket!
OK, heres MY take on the market in general. ANY Cobra with a 427 side oiler is going to be more desirable with that motor. There are some people (like me) that are specifically looking for that. Pretty hard to find one under 50K, all though it CAN be done.
Two ERA's on Cobra Country stand out:
The FIA small block car at mid 40's is a GREAT buy!
The 390 FE at around the same price is "OK", but no question the 390 hurts it's value.
Occasionally you will find an ERA under 40K, and it will ALWAYS have either certain "undesireable" options, is OLD, or needs TLC. Mine needed a LOT of TLC and is OLD, but it has the 427 and I'm very happy. I rebuilt the IRS, new clutch, starter, worked over the trans, carbs, etc. You get what you pay for!