I was a bit skeptical of the 4.5 oz. number for the diesel. A Fox .35 is 6.4 oz, and that is really light. So I went and looked. If the plans are calling out an Allen-Mercury AM35, that is actually a 3.5 cc engine, or a .21 cu. in. displacement. So maybe the 4.5 oz. reported in Model Engine News is correct. As a further comparison, the OS .46LA is right at 9.52 oz., or about a quarter oz. more that your Glowchief .29.
Some quick math using your supplied weights and a nominal moment arm of 6-5/16" for the stock engine location (ref. to cylinder centerline), says you'd have to move the engine back 3-1/4" to get back to the same mass moment. That's huge, and does not seem reasonable. (It would be somewhat less since you'd be moving the prop, fuel tank, and some of the nose structure, etc.) Other assumptions as discussed previously.
Instead, if you used the heavier engine with the CGs in about the same place, you would have to add 1.5 oz. of tail weight at an arm of 20" from the airplane's CG. You'll have to decide if you think the plane can carry roughly 6-1/4 oz. more than the plans prototype. If you had a weight target of say, 36 ounces for a stock configuration, you would be adding almost 18% to the flying weight.
You gave the wingspan as 45". What is the wing area? Could you mount tail weight further back that 20" from the airplane's balance point?
Are you anticipating this will be a "goes around in circles" airplane, or that it will do at least the Old Time maneuvers?
Dave