The 5.3l is going in this winter.    Nothing fancy done to it.    Other than probably flip the intake so air comes in from the rear of the engine.  I have a th350 for it.  But I haven't decided.   I really like my t-18s first gear, it just shifts like a tank
Probably do some tube repairs  They seem to dent,and bend so easily these days😂
And rework some of the tube that protected the 258 , so the 5.3 will get in there
It never ends , but as a hobby , I do enjoy working on it.   Modifiying it, trying to make little improvements here and there 
Then go beat it like a rented mule.    The wife Can't understand why I work so hard on something, and then go out and seemingly try to destroy it.      Makes perfect sense to me though 😳