reguarding putting in a brisson 2.4, I am installing an FPE 2.4 and yes there is room. Of course it will require cutting more of the underside of the cowl away. Also, you will need to make your own stand offs. I needed 1 and 5/8" to bring the engine out far enough. I am still mounting the engine and have not yet begun to cut the cowl.
If you check back in the thread you will find posts by MGA, Bob Forest. He has already done this modification and his posts are very helpful with lots of pics. Also, I have e-mailed him directly with specific questions, which he has been very accommodateing in answering. Really a great guy.
Let me know if I can be of help.