and a matching rear bumper completed the change. New US headlight height regulations also meant that the headlamps were too low. Rather than redesign the front of the car, British Leyland raised the car's suspension by . This, in combination with the new, far heavier bumpers, resulted in significantly poorer handling. For the 1975 model year only, the front anti-roll bar was deleted as a cost-saving measure (though still available as an option). The damage done by the British Leyland response to US legislation was partially alleviated by revisions to the suspension geometry in 1977, when a rear anti-roll bar was made standard equipment on all models. US emissions regulations also reduced horsepower. In March 1979 British Leyland started the production of black painted limited edition MGB roadsters for the US market, meant for a total of 500 examples. Due to a high demand for the limited edition model, production ended with 6,682 examples. The UK received bronze-painted roadsters and a silver GT model limited edition. The production run of homemarket limited edition MGBs was split between 421 roadsters and 579 GTs. The last MGB roadster produced at Abingdon returned to Abingdon County Hall Museum on 1 December 2011, with the help of British Motor Heritage. It was lifted up 30 feet through a first floor window of the Grade I listed building with inches to spare and now forms part of the collection on display in the main gallery. Work on a successor for the MGB had been undertaken as early as 1964 with the EX234, but due to the excellent sales of the MGB and Midget, BMC cancelled it in 1966. In 1968 a second proposed replacement was developed, the ADO76, but British Leyland had ceased work on that project by the end of 1970; the ADO76 would ultimately become the rubber-bumper version of the MGB in 1974. When the Abingdon factory finally closed in late 1980, British Leyland did not replace it, with the EX234 prototype finally being sold at auction in 2016. The decision to discontinue the MGB came about largely due to the poor sales performance of the Triumph TR7, which had largely taken over as BL's contemporary offering in the small sports car market. BL management felt that continued production of the MGB was cannibalising the TR7's sales and this therefore was a justification for taking it off the market. However the TR7 failed