You'll need a complete Pontiac 400 V8 swap kit designed for a 1975 Firebird. This kit will include:
* Motor mounts: These are specifically designed for the 400's dimensions and weight. They won't be in the same place as the original six-cylinder mounts. They'll likely bolt to the frame and/or subframe, often requiring new holes to be drilled.
* Transmission mount: This will also need to be replaced as the transmission and its bellhousing are different.
* Possibly new crossmember: The original crossmember may not be strong enough or positioned correctly for the V8's weight and size. A reinforced or replacement crossmember is frequently necessary.
* Exhaust system: The exhaust system from a six-cylinder won't fit a V8.
Don't try to adapt the existing six-cylinder mounts. Doing so will be unsafe and likely result in engine damage or failure. The stress on the frame and mounts would be immense, leading to potential accidents.
Finding the correct parts:
Look for swap kits specifically advertised for a "1975 Pontiac Firebird 400 V8 swap." Several reputable suppliers specialize in these kits. Searching online (e.g., on eBay, Summit Racing, Jegs) will yield numerous results. Read reviews carefully before purchasing to ensure you get a high-quality kit.
Remember, this is a significant engine swap requiring mechanical expertise. If you're not experienced with engine swaps, consider seeking professional help from a mechanic specializing in classic car restorations. Improper installation could lead to serious damage or injury.
