I am not fan of automotive piston engines for aircraft use
as the design and materials used are not up to the
continuous power required by an aircraft engine.  They
could fail in a catastrophic fashion without warning.
There is a real reason why only the finest steels and
manufacturing processes are used in real aircraft engines.
For that reason I decline to provide any help.

Read may article on the subject here.
http://www.rotaryeng.net/Rotor-v-Piston.html

Also obtain and read this book.

Sky Ranch Engineering Manual. This book presents an excellent
overview of the problems of aircraft engines. It is 500  pages and a
bargain at only $23. There are many details on the materials and
processes used to build a successful aircraft engine. There is a
very good and exhaustive discussion of destructive  torsional
vibrations and fatigue. The telephone number  to buy this book is
(916) 421 7672. The author is John Schwaner. John is highly thought
of in the experimental aircraft community.

Do not kill the messenger :)

Paul Lamar

Paul, With the rads mounted so close to the cowl, how would you ever get
enough flow through them, or even get a diffuser/wedge to supply air? I
guess you could always install cowl louvers like we used to put on the Hot
Rods... ;))

Rick in Alaska