With a tremendous 40-car entry of sports, saloon and GT cars of the 1960s and 1970s, the fifth race in the 2008 Heritage Grand Touring Car Challenge should deliver a great spectacle at Silverstone on Saturday (31 May).The spectacular series of races for period machinery is an incredibly popular part of the British motor racing scene, with cars ranging from Mini Coopers to Ford Mustangs and from Jaguar E Types to Sunbeam Tigers and Aston Martin V8s. The bigger cars have more power than grip, so the action is always fast and furious and the two-driver format makes for some great racing.Likely to be among the quickest of all, and determined to add another win to their impressive tally, will be Chris Beighton and Jon Finnemore in their stunningly quick Sunbeam Tiger. They've already bagged a win and two seconds from four Heritage races to date this season, but will certainly not have things all their own way at Silverstone.Two very potent Morgan Plus 8s stand out as other major contenders, including that of father and son team Grahame and Oliver Bryant. They took a great victory at Brands during the recent A1GP support races and can certainly win again, while Rick Lloyd and Matthew Wurr will also be strong challengers in their Plus 8.Thundering American V8s are always a popular element of the HGT entry and at least six of them will be on the grid at Silverstone. Alec Hammond is a leading runner in the Chevrolet Camaro he shares with veteran racer Graham Hathaway, and the Ford Mustang of father and daughter Robin and Zoe North is also very rapid, as is the Chevrolet Camaro of Arthur Thurtle/Roger Bennington. A real dark horse could be the Mustang of Bob Pepper, who has enlisted the driving talents of GT ace Neil Cunningham to share the car, while the Jaguar E Type of Mike Luck and Jonathan Edwards cannot be discounted in the chase for the podium.In class C for the less modified V8s, the hard-charging MGB GTV8 of Roy McCarthy will be the benchmark and he’s likely to be up among the very fastest cars in the race. The Jaguar E Type of Andy Jenkinson and John Young will be quick from class C, while Grahame Bull has enlisted the services of former single-seater ace David Coyne to share his E Type.A stunning line-up of six-cylinder Aston Martins will contest their own class within the 50-minute race, with the leading contenders sure to include Howard Spooner, Peter Wheeler/Ben Samuelson and Ian McCallum/John Bussell.Finally, two classes for the less powerful cars will produce races within the race, with the Ford Escort of Tim Glover/Rikki Cann set to be top of class B as the Mini Cooper of Harvey and Clive Death takes on the BMW 2002 of Bob Godbold/Anthony Matthews in class A.