not necessarily apples and oranges with your R and my Ford 392 crate stroker . IF you have the space, go with a 1" spacer if you can . I added one to my engine , Pro Sytstems custom 780 Holley , single plane high rise manifold , replacing the 1/4" spacer that was there ....and on a Mustang brand chassis dyno it added almost 20 rwhp as well as 20 more in torque . NO fuel boiling issues either . i have just a hair room left of space under the hood/scoop, but it does not touch . It is some type of
synthetic material, plastic like .
Also, if limited space, Holley offers a very thin aluminum heat deflector that has worked well on some cars , but not sure it cures all the ills on all engines . Mine is the size of the base of the carb, the Holley aluminum one is larger than the base and helps dissipate the heat as well as its size deflecting alot of the heat .
Bill