I have a ef falcon with a au xr6 Engine the engine has a cracked oil ring its blowing clouds of white smoke on de accelaration . I want to replace the motor should I get a average k au bottom end and put my tickford head on it or use a ef botom end and use my tickfordhead what would be better in performance

Car has these mods

Shift kitted auto
4:11 LSD
Pacemaker 2 1/2 inch single exhaust
Au xr6 Tickford engine with larger exhuat ports
440cc injectors


Ef bottom end or au bottom what one should I use

Au falcon has a higher compression ratio and is screwed together better. Au is newer than an e series engine

Have you got a J3 chip or similar aftermarket ECU for using those bigger injectors ???
If not, then you will be having a "bore wash" problem, thinning the oil, and buggering the engine in general.
Oil rings don't crack....they get gummed up however, from lack of servicing.

Why are you using 42lb injectors? they are twice the size you need for 4.0L NA, and with the small mods you have they are not required. As cjh said, you will overfuel and stuff you oil and the engine.