Question about upgrading a 1966 Mustang?
the nice thing about ownng a nice classic is its yours to do with as you want, there are many websites that have mustang stuff, from stock parts to the latest and greatest 450 horsebower BOSS 351 V8 which would fit perfectly in your car. I will type a list of names, just type each one in the web search box and click scroll down the results page and click on the links that look good. Roush Performance.com is a huge company that makes custom parts for newer mustangs, but many of the engines and transmissions will fit in your car. Summitracing.com will have some performance parts for your car, and a lot of others, Jegs.com is a good website, Year one.com is an excellent place for top quality parts, however its not the el cheapo stuff, they pride thier self on better than stock in some cases so a lot depends on what you want to do. And if you type " 1966 mustang parts ? " in your web search box and the results page will have thousands of links, I mentioned a few of the bigger sites that I know have a good reputation. Be careful who you order parts from.
Here is a classic online magazine that will have a lot of information on all kinds of cars, Hemmings.com has been around for many years and the online web site has thousands of links to articles , websites, wrecking yards, cars for sale, parts for sale , you name it, and hemmings motor news is the car lovers dream. I am familiar with the mustang and many classic cars, there are lots of good engines and transmissions for your car the only limitation is money, but you could have a modern 5.0 installed with fuel injection and a four speed automatic and have a fun car to drive with decent gas mileage. Or you can find a 289 which is a v8 that was common in mustangs in 66 with a carburetor or the 302 and make a nice fun car to drive with decent fuel miles per gallon, its all up to your pocket book, anyhow have fun parts searching.