Fitting:
Three bolts in a horizontal line under the dash top for a roadster, two for a GT as here. There should be two larger elongated washers AFH2627 for the upper rear wing bolts as shown here:
And this clamp plate AHH8094 (GT only) where the wing attaches to the A-post:
Both the above from mgb-gt.co.uk
Four more in a vertical line by the A-post, three spire clips along the bottom edge of the sill for the wing lower-edge screws, three to the front apron under the headlight, two behind the grille, and finally the line along the channel beside the bonnet.
Fitting kits for the sill part are very variable in what they contain, some only conventional nuts, washers and bolts. There are three elongated washers AFH2546 for the lower edge of the wing as shown here, although there is an opinion that these should be between the wing and the sill for drainage and ventilation as well as getting rust protection such as Dinitrol in the gap: (John Keene)
The wing seam has a dog-leg on both roadster and GT although it is concealed by the screen seal on a roadster. The wing must be pushed back as far as it will go to close up any gaps beside the seam. There was something preventing that here, found like this, as shown by the screen seal witness marks: (MG Experience)
When preparing Bee for her repaint in 1991 I noticed that the grille was only slightly recessed from the wing on the nearside whereas it was significantly recessed on the offside but only at the bottom. The grille seemed to be aligned with the apron and bonnet, so it must be the wing. I removed the lower bolt from the inner wing to the wing and could push the wing back quite easily, but that put the lower holes way out of line. I elongated the hole in the inner wing, pushed the wing back to align with the grille like the nearside, and tightened the lower bolt to hold it in place. The leading edge of the inner wing has been dressed back to lie against the outer wing (upper arrow). Compare with the nearside:
The offside wing is a still a bit forwards of the bonnet and the grille, but at least the grille is recessed by the same amount top to bottom both sides. Before this the lower part of the grille on the offside was recessed by a good inch:
Another issue pre-paint was that I couldn't get the crease in the door skin (under which the bright trim strip fits) to line up with both the front and rear wings without cocking the door in the opening, which looked awful. The wing crease was too high, so I slackened the three bolts in the vertical line by the A-post, and with the car under the carport put a length of timber on top of the wing above those bolts. Put a jack under the castle rail under those bolts ... and jacked the car up. This pushed the wing down relative to the rest of the car, and when in line I tightened the three bolts, and there it has stayed.
August 2022: Complaints on the MGOC forum of replacement grilles being too wide for the gap between the wings. The problem seems to be the 'U'-channel that forms the grill surround has not been fully formed, the outer flange sticks sticks out at an angle instead of pointing straight back so fouling the wings. Ventilation pipe crimps were used here to force the flange to 'lie down' at the corners: (John Keane)
Bee's has the 'U' fully-formed with the flange at right-angles to the front face and parallel with the sides of the aperture giving a clearance to the wing, even at the top corners. This also shows the honeycomb with the raised diagonals going from upper left to lower right:
Incidentally 30 years ago Bee's was as shiny as John's.
More information on radiator grilles here.