Genuine Porsche RS 18" 3 piece split rim Speedline wheels

[jbl930]

I have the opportunity to purchase a set of Genuine Porsche RS 18" 3 piece split rim Speedline wheels F8" R10", the part numbers are Front 99336213681 Rears 99336214081. My question is are these a direct bolt on replacement on my 87 euro 930 or is there a lot of work involved, also what size tyres would I need to fit. Thanks Guys

[jimmy riviera]

tyres are 225 up front and 265 at the back