You know how Abarth’s heated up Fiat 500 seems to get a monthly special edition? That time may have dawned for the Abarth 124 Spider , too. This is the 124 GT, and there are some key changes afoot. The biggest change you’ll have likely spotted: it now comes with a hard top. It’s a bit of a homage to the Abarth 124 Rally of the 1970s. While that car came with a fixed roof, the 124 GT’s is removable. It’s not a limited-run special, and there’s no official price yet, but expect a ten per cent premium over a soft-top Abarth 124. So around £33,000 seems likely.There’s no trick folding hard-top stuff here: it’s one, large item, with a big wraparound rear screen that boosts visibility. The regular soft top lurks beneath in case it rains while you’re out. Yep, you’ll need somewhere to store the roof too. Worth bearing in mind if you park your car on the street… Made of carbonfibre, the roof weighs 16kg. So it’ll be a bit cumbersome to get on and off, and with a variety of screws to undo, a minor rigmarole as well. The weight gain is counteracted by another of the 124 GT’s changes: it gets new lightweight 17in alloy wheels, which save around 4kg a corner. That means the 124 Spider’s claimed 1,060kg kerb weight carries over, though you can expect the centre of gravity to have risen. Weight distribution remains a perfect 50/50 front/rear. Mind, once you lose the roof you’ll suddenly have a purist’s 124 that’s 16kg lighter than normal and with the centre of gravity dropped back down. The GT has no suspension changes; Abarth claims a slight improvement in torsional rigidity with the roof in place, but doesn’t provide actual figures.Nope. But it’s still more than brisk enough. It uses the 168bhp 1.4-litre turbo four from the 124 Spider, and with the same claimed weight, offers an identical 6.8sec 0-62mph time and 144mph top speed. You can expect CO2 and mpg to be unchanged, too. It still sounds outrageous, thanks to the standard ‘Record Monza’ sports exhaust. But this time its shouty persona is most evident to those outside. The Abarth 124 has always been an utterly raucous-sounding car, but with the hard top in place, it’s a bit muted inside. A bit like wearing a particularly large pair of headphones on a train and dulling the hubbub around you. The end result is that it feels a bit more grown up. Less shouty in traffic, less droney on the motorway, with only a bit of wind rustle at motorway speeds to give away the fact the roof isn’t permanently fixed.You’d be a more astute – or sensitive – person than me to be able to decipher any real chassis differences. The steering is perhaps a little lighter, by virtue of those lighter wheels, but even having driven a normal Abarth 124 soft-top back-to-back with the 124 GT, there’s next to no difference between the two. So all the 124’s great bits – its mischievous rear-drive handling, fabulous manual gearshift and thumping acceleration – remain. It’s joyously frisky to drive when you’re in the mood, egged on by the bright red rev counter, quick steering and the underlying burble of exhaust. It remains a stiff car, and a bit unyielding over really bumpy roads. So while there’s more aural luxury with that hard top in place, the ride hasn’t come over all soft to accompany the hush.It all depends. Abarth wasn’t keen for us to have a go at taking the roof off, and the amount of screws that need undoing – and the nooks and crannies a couple of them are in – suggest you won’t be flipping the hard top on and off on a whim. You’ll probably remove it when the clocks go forward in spring and forget about it until the clocks go back and autumn’s setting in. Providing you’ve got somewhere to store it, that is. There are other changes to justify the cost, mind. There’s a posh Bose stereo and you can have Abarth’s rally-inspired heritage colour schemes for free. There’s the small matter of how much cooler it looks with a hard top, too. Far more reminiscent of Abarth rally cars past and present. Which rather makes us think it would be more convincing with a bit of extra power to accompany its other changes. We asked an Abarth insider if it had been considered, and they suggested the 187bhp possessed by the fruitiest 500s (known as Abarth 695 s) wouldn’t be a big enough leap, and that something closer to 200bhp might be in development for future 124s. Abarth’s penchant for a special edition suggests this 124 GT is probably the first step on the way there. It’s as fun (and flawed) as ever, just make sure you’ve got somewhere to put the roof…