318 LA roller block questions

Hello guys.. I'm technically a B-body owner but this forum is amazing so here i am :) Just a quick question or 2

I just picked up a 318 of FB (have never run a small block before though it would be fun to play with) What i ended up with was a '85 LA with the spider mounts in the valley but a flat tappet cam in it. It was a truck motor, i did some research and couldn't find much other than this is possible to find now and then.

I was mainly wondering if there is any reason to avoid using this before i start dumping money into parts? Plan is to get heads/cam/intake setup for this year to get the car working and sorted (hasn't moved since 1978, going through every bolt) Then hopefully a 390 next year.
P.S. I don't plan on a massive cam as it will be a street car to have fun in and beat on, not heading to the strip.. Any issues using factory roller lifters upto around .525? thanks guys.
On my stock Magnum (stock head gaskets )Which I installed a cam in, I have a .512 lift cam hyd lifter roller, which has about 20 thousandths clearance between the retainer and valve guide.
2 choices, cut the guide down or get Hughes retainers which will allow more lift