To Mod or Not ?

When it comes to working on others vehicles I don't have a problem but I i'm getting ready to start a '74 Scamp project and wonder if doing some custom mods would be welcomed and possibly help the resale... may I have your opinion please?

I first have to replace the top due to a failed vinyl causing cancer. The motor is a 318 roller that has been bored to 323 CI, head work, intake, 4 bbl, backed by an automatic. I will also do the simple suspension tricks for a track car. The goal is to have a sweet looking low stance cruiser.

I wonder about:

1. Many like the '70-'72 bumpers- I was shocked to find out that the rear panel cost $380, then add the cost of the bumper, hardware, and lower panel... this might be too costly to break even... but what do you think?

2. The rear quarter panel extensions: fill the seams or leave them?

3. I have never really liked the exposed gas cap. Make a flat cap or recess the nozzle and add a gas door, or leave it alone ?

4. Vinyl top or not?

5. Engine compartment: relocate the battery, hide the wires, smooth all panels, cold air system either going up to the radiator core or back to the cowl (cutting a oblong hole in the firewall to access the area under the windshield)

6. The seats have already been covered in light grey vinyl with dark grey inserts... I was thinking of Inferno Red or a wine color... ?

I plan on driving this until someone else "has to have it" so I don't want to go overboard with custom work.... that can be saved for another project.
Thank you for your opinions!