The 273 was perfectly reliable. Mine had 250,000 miles before it finally popped. When I went to rebuild it the pistons were not available at the time as they're made in batches and sometimes not available.
The '64-'65 273 had slightly different threaded bolt patterns for the intake manifold. The '66 273 and then 318s and later used an intake manifold with different angles for the bolts. You can choose to either:
a) Find an Edelbrock D4B intake manifold and call it a day
b) Get a later LD4B and modify the mounting holes
If you go with a 318, then the LD4B or Weiand intake would be a good choice.
Look for a pair of casting #302 heads. The 273 is all about port velocity, not volume. The #302 heads are great and not too hard to find. They can be found here in the wand-ads or very often at Wildcat.
Personally I like a hydraulic cam (less maintenance) and an Edelbrock 500cfm carb. The Eddies aren't the best performers, but they're easy to tune and hold it well. I always install a air/fuel ratio gauge so dialing in a carb is very easy. I'm a big fan of the Street Demon carbs but the smallest version (625cfm) is too big for the 273. Or hey, fuel infection. There's some cool threads on a good injection system over here: FiTech EFI system
Any engine rebuilder can do a good job with a 273. At the end of the day it's just another LA small block.
-Red
