Re: 1975 Chieftain Express
That is one big boat!!! How much do they want for it? Everything you mention can easily be fixed/reno if you are handy....
Seats - $400-1000
Floor - $400-600 on that big a boat
All plus your time
See how much help the trailer needs - bearings, winch, rollers, tires, electric - you can often dump an easy $500 into a trailer to make it road worthy again.
As far as the drive train - I tend to be no as scared of the I/O's as some - the motor might need a valve/ring job - but any local shop can do that - but alternator/battery/starter can all add up - I would count on those needing rebuilds - solenoids etc. The carb will need to be cleaned.
Make sure their are no winterization issues.
As far as the outdrive - same thing - is it cracked - count on 300-500 to put new cables/bellows/impeller in if everything elese is cool.
All above is easy to do - but add it up so you know what you are dealing with.
Read this pack of threads:
http://forums.iboats.com/showthread.php?t=385090
Is everything there and work? Bilge pump, lights, gauges, trim and tilt