What do mean by "rebuilding"? Are you really going through the engine thouroghly, or just new gaskets for the intake and exhaust? What kind of budget are you working with. What kind of driving are you planning to do?
Some mods make HP at the top end while taking from the bottom.
But if I were building a cam in block 4 banger here's where I would spend my money.
1. Make sure the lower end is in good shape, bearings are fresh, Oil pump is working well and so on.
2. If the budget allows, low friction ceramic coatings for the sides of the pistons, possibly heat coating the tops of the pistons.
3. Mill the head down a few thousands to raise compression. (5-10hp)
4. If nothing else, port match the head and manifolds. The Sunbeam had fairly good crossflow heads, but good power can be made with a little judicious use of a dremel tool. Of course the best power will come from porting and polishing, but this is best left to a machine shop with a flow bench (this can run into SERIOUS $$$$). (Port matching 5-10 hp, Real porting and polishing 10-25 hp)
5. A good extractor type header (does anybody make these for the Alpine anymore?). Couple that with a good free flow exhaust system. (10-15 hp)
6. Cam (need I say more?) if you can find one. (7-15 hp)
7. Last on the big list is get rid of the Strombergs and move to Weber Side draughts. (10-20 hp)
8. Of the smaller items, use a K&N cone type filter on each carb (5-7 hp)
These mods will sacrifice some of the bottom end torque but get you bigger gains on the top. Also some mods depend on other mods. Most notably, in order to get full effect from the Webers you need free flow exhaust with a header. You should have the exhaust, carbs and head done before changing the Cam.
The electric fan won't make you any extra power, but it will keep the engine from using those 2 or 3 hp to turn a mechanical fan. I never used Grose Jets on my Sunbeam, but in my MG's the had effect on power other then to keep the carbs from loading up. A much better system of regulating flow then rubber points on brass seats.
You might be able to adance the timing a couple degrees, but you'll probably need to run premium to keep from knocking.
If I remember right the stock MKI and MKII (the Alpines I had) had about 100 hp. Doing all the mods above could get you an extra 50-75 hp on the earlier 1498cc engine.
Steve Hoult '89 MR2 SC ASP9N www.mr2sc.com Got Boost?