Yes spend the extra and get the Optima, what a difference while cranking. It does sit side ways in the original box but stays in nice/tight after adding a piece of wood under some rubber shims.
The Optima Red Top 6 v is well worth the price. Bought one about a year ago for my 36 Cabriolet. Car starts quicker and seems to run better with the Optima. You can order direct from Optma.