I've been remembering long engines put in place of short ones that have come through the shop and the results were not sterling. There was a 1930 Plymouth 4 cyl with a 258 American Motors I6, a 1928 Chevy 4 cyl dump truck with a 216, and a WW2 Jeep with a twin cam 4.2 Jaguar I6. The Plymouth had been a taxi in Mexico and was a mess with a Rube Goldberg engine and transmission install, the dump truck was used in a gold mine and I wasn't about to ridicule the install because the driver used the back of the exhaust manifold as a gas pedal foot rest and had to be way tougher than me, and the Jeep/Jag project was beautiful but not good as a hunting vehicle for which it was intended; great cruiser. If you can do a sanitary install and keep in mind the weight/geometry changes Jon brought up you could have neat project. The exhaust sound of a Buick straight eight is in a class by itself. Good luck.
