Well done Uni! Hope you got a bargain...
Patina appears original, The red may have been touched up. Bars and tank look light or touched but may be the Image. Also appears to be showing remnants of the original plating on the axles.
A tidy little Model 5 Series 1.
New repro,
Tap...No...Ebay or private. ..Your looking for a CC branding. Price 10-25 depending on cond.
Wheels...No, but may occasionally be bought of ebay for high prices. 150-200 a set.
Snorkel...Yes and No...Some places list for later 60s Models and are close, but good Sh ones can also be bought of ebay 15-30 range
Pistons and rings all gaskets seals and bearings are available here on the ODK online store and competetive prices.
An Engine number if correct will determine age and accuracy.
Also a pull start will be a nice addition as will a special badge and groove cover If yow want to Max it out.
Std recoil Pull start cost 20-45 on condition.
badge 50-100 depending on cond...80 should get you a tidy crack free minimum chip/marks.
Carby should also be Victa stamped with CC behind the primer pin.
3/4 Throttle issues are very common,
Incorrect cable positioning, It may be running full, but has slack left. Can be adjusted at carb.
If its backfiring when 3/4 is reached its taking to much air. Block the snorkel partially while its at 3/4 and see if it smooths out as you slowly choke it.
otherwise strip the carb and check float clearance as it may be starving at hig speed messing up the air fuel ratio.
also check needle and main jet for previous damage or jet damage.
The Mower uses Whitworth and AF. Ill check on all the sizes you need but 1/4 and 5/16 w are the most common with 1/2 AF Another. Ill get you allbthe spanner and tapping thread sizes.
Anyways have fun with your new toy, shes going to come up a treat.
Any questions you Have please post away!!!

Cant see you air filter assy for accuracy.