Yes, the Spark has P/E parts for the hod pins and wires. The Spark also has the more accurately cast wheels.
Minichamps also did a very nice version with opening engine cover and engine detail. This also has separately cast hood pins and cables :
If you like the engine detail but don't want to pay Minichamps money, there is always the Bang version. However, there are no bonnet pin cables, though at least the wheels are correct even if they are the wrong colour. Like a lot of Bang, this one may be a bit under-scale and will look a little small when displayed alongside other GT40's :
From the same era as the Bang (ie 15 years ago) was this OXA. I don't know much about OXA and the only models they appear to have done were a set of GT40's. No opening parts or P/E trim, but the shape was pretty good and you get accurate wheels.
Solido have also had a go at the GT40. Its pretty basic, as you'd expect at their price point, and the wheels look too small. It is possible this may be based on the old Universal Hobbies / Eagles Race casting :
Another cheap option is the Del Prado version. Sold in blister packs, this can often be found for $10 or less. If you want a cheap GT40 in your collection and aren't too fussed about the detail, this is good value for money if you get one at the right price.
One interesting difference in all the above is that the IXO has Firestone tyres, while just about everyone else have Goodyear markings. From photos I've seen, the car started on the Firestones (in the dry), but switched to Goodyears (in the wet). While both are correct, if the general rule of thumb is to model the car as it started the race, this makes the IXO more accurate.