Legalities regarding fuel tank / filler placement

[richardpope50]

I see I put a 'not' in when I should not have so above is correct re IVA.

The IVA and the DVLA registration plate are two separate things. If you need an IVA, the car is treated as new so you need a new registration plate. But if you have enough points then you are given a registration number for the same year as your donor + engine but cannot keep the actual donor's registration number*. The points confirm that you have used the donor and its engine.

If you do not have enough points it is assumed you have used various bits and cannot use an age related plate and have to have a Q plate.

If you pass an IVA test, you do not need an MOT for three years as per a new car.

*This is all tied up with a kit conversion and commonly applies to kit cars. If all you are doing is modifying a chassis, then this is not but you will need an IVA test as explained above and I think (I'm sure) you can keep.your registration. If you used your MGB as a donor for an MGB based kit, it's a kit car.

Sounds as though none of this applies to you. Also, I do not think an MOT guy looks at a fuel tank being in the passenger' cabin. It would, I guess, only apply if it was being inspected and probably relating to some claim.