My preference is for a solid flat tappet, but that is because I am doing all I can to reduce the number of potential points of failure. I also have a late LA360 block which came with a hydraulic roller but I am not going that route. I suspect that since you are going with a 4" stroke, you won't be revving as high as I plan to with my 3.58" stroke. And therefore a hydraulic roller would work fine for you.
You may want to read this article;
#2---Choosing a Cam
You may want to pick your converter after you have your cam by contacting a converter company and giving them all the info on your build. They can set you up.
