why is1998 dodge neon is over heating?

[Jay S]

i have a 1998 dodge neon that we have turned into a racecar to run on local dirt tracks...it runs super and runs in top 3 usually...here is problem we are having engine over heats and leaks oil...if car sits and idles it will not over heat but you get out on track and usually within 5-6 laps on 1/4 mile track it starts getting hot and steaming,,have put brandnew radiator in it...and thermostat has middle cut out of it for better flow...fans are wired direct on toggle switch and run all the time...looks like there is good flow through radiator ..also when car is idling for long time in drive way it will start leaking oil looks like it is coming from rear main seal area but we have never had to add oil to it and doesnt look like there is any water in it or and oil in water...suggestions? will block seal or something work ? have already put rear main seal stop leak in it but didnt seam like it works...also seems like it has to run awhile for it to stop leaking oil...remember this a is a dirttrack car and not driven but once a week and maybe 10 miles total for a race weekend