The Indy RX-5 is designed around the Mazda / Miata MX-5 mk 2. This is the 1999 - 2000 1.8 model.
This comes in several specific models such as:
""S"" or ""Sport"" - this is a 1.8 litre engine with a Limited Slip Differential (Torsion) and a 5 speed gearbox as standard
""ICON"" - this is a 1.8 litre engine with a Limited Slip Differential and a 6 speed gearbox.
The standard 1.8 base model MX-5 required is a 1.8 open differential version.
The manual has been written with the 1.8 engine from the mk 2 in mind, however it is possible to use the 1.8 mk 2.5 VVT engine.
The differences betwen the 1.8 mk 2 and mk 2.5 is the bigger brakes on the mk 2.5, the VVT engine (which produces another 10 bhp as standard). We have several customers who have built RX-5's on the mk 2.5 so we know it can be done.
We also have builders who have use the mk 1 and the 1.6, however this engine choice isn't something we would support, but we know it can be done.