You've got quite a few options.
One is to follow
Crosley's lead, but since you don;t have D7 heads in Australia, just mill the later model 250 XA-XB head down, and fit a 2300 series Holley on via two bolt adaptor so you don't warp and crack the log head. You need to take the Power valve chanel restrictions down from 59 thou on the 320/350 series to about 40 thou or less by shoving a wire in both holes. On the 500 cfm, they have two 62 thou PVCR's. Then run 6.5 power valve or less. Jet it down to 56 a s a start on the 350, and about 65 if you use a 500 cfm carb.
Use the later XE electronic ignition, or the XF unleaded TFI electronic ignition, and have a green XF ULP Bosch MAF sensor on the manifold and an XF front right hand side stund mounted knock sensor shoved on the front of the and run the EECIV module. That will allow you to run ignition fully advanced to 40 degrees and then backed off to a better 34 degrees under load.
Details? For Aussie X-flows from 1986 to the last XF Falcon Ute and Nissan Ute in early 1992, its E6RF 12A69BA, and is now a defuct part.Down here in Australasia, our big sensor company for Air Temperature Sensors,Coolant Temperature Sensors, Crank Angle Sensors ,Idle Air Control Motors, Knock Sensors, Map Sensors, Power Steering Switches and Throttle Position Switches is ACA Engine Management Solutions®
ACA dont list it any more, but they do list the later EEC 5 sensors for most OHC 6's and US derived Mustang GT and Explorer GT40 V8'S. See page 50 (44 to 46 on the file, but listed 50)
http://www.mazdabg.com/ftp-uploads/MAZD ... alogue.pdf
The common E6RF 12A69BA sensor is the orange or black inserted item in one of
XFlow_Fairlane's posts
Other photos from Fordmods

They look similar to the US stuff but aren't. The Australian XF item is two wire, and is just a tell tale for 0 to 150 Hz knock. When knock is present, it sends 3 volts to the 60 pin EEC IV computer, just like the early 1981 US Windsor 351 with there 145 hp EEC3 5.8's, and cancels off some advance.
But I'd look at
Ken Van Accolyen's method of mounting the carb on a Tranadapt 2044 adaptor, and just use the stock 250 log with a 500 Holley. Open the hole up to 1.875". In order to get things under the hood, you can trim off the choke horn, and use the aviation Tom McNeilly throttle lean device, and never have to change the jets again. It produces 150% rich on straight up setting, then about 1/4 turn or so in a position that has to be determined by time on an exhast gas analyser or dyno , it drops back to the required jet size. If you do a dyno run with this, you could produce optimum jetting by measuring the degrees of movement of the carb float mounted crank. For cold starts, it would get shifted upright via a bowden cable, and then throttled back to that positively stopped position when its warmed up. Its like a Percy's adjustajet, but it produces a much better 'roosters tail' of fuel atomisation. 2-bbl Holleys aren't great at fuel distribution, but the kit is from
tomcn@earthlink.net for US $150 dollars excluding post and packaging.These are throttle leaning devices used for light aircraft
-Tom McNeilly
14001 East Williams Field Rd.
Gilbert, AZ 85296
International phone number is +1-602-899-7613
He's in Arizona, USA.
Northwest Aero Products also has them available. They are at
13812 179th Avenue SE
Monroe, WA 98272
International phone number +1-360-805-8183
Call displayed telephone number to ask for respective email address of Northwest Aero Products.
Follow those recomendations and you'll be able to adjust total jetting while still using the power valve. A knock sensor and MAF sensor are cheap junkyard XF ulp stuff you can get of any 1988-1991 XF Falcon GLS 4.1 ute or Nissan Ute. They will help you out.
That's what I've done with mine. Then you can cam it up when dollars allow.
For air cleaner base, use Dale Wilches awesome spun aluminum 1 3/8 offset and 2" drop air cleaner base.
http://www.ebay.com/itm/Offset-air-clea ... 0456237704



The Key is that the engine is undercarbed, ignition needs to be custom tuned which you can with TFI, and once you got the ability to adjust air fuel and retard back igntion to avoid the big bang, your made. You can go up, up, up on compression then, with a shaved head and start playing with the cam.