A compact support.
Keep its limits visible.

A folded channel beneath the mount pair

The factory mounting illustration shows an upturned cradle edge and elongated openings in the inclined mounting faces. The current native cradle now uses rounded channel folds and centered slots in place of its flat base edges and circular openings. The gearbox, rubber pair, thirteen other support groups and all source placements stay.

The selected 24 mm lip height, 6 mm inside bend radius, 3 mm gauge and 9 × 18 mm slots are construction estimates. The second repeated channel edge is an interpretation of the exploded drawing, not a surveyed CHA266 pressing. Original outline bounds, central floor, fixing centers, gearbox pad faces and body/tunnel axis lines stay. Slot centers stay on the previous round-hole axes; this does not establish a fitted adjustment range or a drilling map.

Earlier compact-support reconstruction

What the evidence establishes

The factory mounting plate separates CHA266, two rear rubbers and base/side fixing roles. It distinguishes122689 from CHA615 at GAN6-176236 and calls for CHA615 in pairs. Neither branch is identified as fitted. North American restraint, cable and tie-bar roles remain unselected.

A supplier’s annotated122689/CHA615 photograph gives a34mm maximum body diameter,34mm length between the outer metal faces and17mm exposed studs. Those are catalog comparisons. Its combined label does not resolve the factory change point or identify the car’s actual mounts. The earlier reference used60.96mm metal-face diameter and49.1067mm outer-face spacing.

British Motor Heritage lists2A5478 as the full-width centre-crossmember assembly for1958–79. That establishes a body-panel role, not the dimensions or attachment of a removable gearbox member. Unscaled donor gearbox views support paired inclined mounts at extension pads. Existing owner IMG_6919 and IMG_6341 provide underbody/cabin context without surveying this hidden rear support.

What changed in the construction

The mount centres move along their existing45-degree axes to keep the inner gearbox-pad bearing planes fixed. Maximum diameter and outer-face spacing follow the34mm comparison. The1.5mm face gauges,31mm rubber waist/body and unloaded cylindrical profile remain estimates; the supplier does not specify that internal split.

A rounded246mm cradle-base bearing plane replaces110.0667mm in the construction frame. The beam bottom changes from59.2667 to195.2mm. Beam width, depth, section height and floor-end upper planes stay. The shortened end channels and48×68mm cradle plates are construction hypotheses guided by compact mounting architecture, not fitted sections, welds, dimensions or a verified load path. The broad base outline, tunnel-side holes and long-bolt axis lines stay. The retained base-axis Y coordinate is an arbitrary point on a vertical line, not the new bearing-plane station.

The estimated inclined bores continue through crossing webs. Separate smooth studs and88.9mm long-bolt comparisons retain explicit limits: no verified thread, engagement, torque, bond or compression. The raised long bolts follow the revised beam underside without changing their length. No exhaust, cabin, engine or gearbox mesh is trimmed or moved to manufacture clearance.