Stock mostly, but mod if done tastefully.
In my loft I've got Max Power magazines which I bought back in 1994 / 1995. At the time I thought the cars featured were great and the modifications were on the whole pretty

.
These days though - it's difficult to see exactly what the original cover cars are they are buried under so much plastic and stick on carbon fibre. It could be an age thing, but there certainly is a lot of poo type quality modifications out there.
Personally - buy stock and then modify to taste if required.