I have wanted to build a number of mid-60's Indy race cars - 1964 Lotus 34 (modifying the AMT Lotus 29), a 1965 Lotus 38 (from the IMC kit) and a 1968 Gurney Eagle (MPC kit). It would entail quite a lot of work correcting the many inaccuracies if these kits. One of the biggest drawbacks is that the engines in these kits are so poorly molded. There is distinct lack of detail, the size is not correct and the 'bundle of snakes' exhaust is usually a blob of plastic. I have been in touch with Mad Mike (on this forum) and was able to secure three engines that were 3D printed in the correct size for these 1:25 scale kits. Below are some comparison and test fitting photos for these three engines. I'm sure there are a variety of other kits that could use this engine.
1964 Lotus 34 - Here is the Mad Mike engine, compared to the AMT Lotus powered by Ford (Lotus 29) experimental engine. I have never seen a photo of the AMT engine, with these exhaust pipes, on any race car. The AMT engine is a bit undersized.
Here is the engine, test fitting into the AMT chassis, it needs to be lowered a bit and a transmission added.
1965 Lotus 38 - Jimmy Clark Indy 500 winner, from IMC kit. The exhaust 'blob' is replaced by 3D printed pipes.
Here is the engine test fitted into the IMC chassis
1968 Gurney Eagle - MPC kit comparing the two engines. The transmissions is extremely well done.
Here is the engine test fitted into the MPC chassis